Science.gov

Sample records for 5-mw rcs-based short-pulse

  1. Short pulse test set

    NASA Astrophysics Data System (ADS)

    1990-11-01

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

  2. Short 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.

  3. 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)

  4. Demonstration of 5MW PAFC power plant

    SciTech Connect

    Usami, Yutaka; Takae, Toshio

    1996-12-31

    Phosphoric Acid Fuel Cell Technology Research Association, established in May 1991 by Japanese 10 electric power and 4 gas companies, started a new project in 1991 FY, with the object of PAFC realization and aiming the development of 5MW- class PAFC. power plant for urban energy center and 1 MW- class power plant for onsite use. This project is carried out as 6 years plan jointly with New Energy and Industrial Technology Development Organization. The targets of the project are to evaluate and resolve the development task, such as a high reliability, compactness and cost reduction throughout the engineering, manufacturing and field testing of PAFC power plants. PAC tests and power generating test operations of 5MW plant were completed in 1994. Conducting the 2 years continuous operations and studies since 1995, the plant operational performance, system control characteristics, waste heat recovery and environmental advantage will be demonstrated.

  5. 5MW Raft River facility experience

    SciTech Connect

    Whitbeck, J.F.

    1980-01-01

    The Raft River geothermal plant is a small binary cycle conversion system which uses isobutane as the working fluid. This plant uses a staged boiler concept to achieve better performance than could be obtained by a single boiler. The plant was designed to operate with a geothermal water inlet temperature of 143/sup 0/C (290/sup 0/F) and produce a nominal generator output of 5MW. The plant is supported by a supply and injection system consisting of three supply wells (about 1524m or 5000 ft deep) and two injection wells (about 1158m or 3800 ft deep). Experience in several important areas: environmental, supply and injection system, and power plant, are discussed. (MHR)

  6. Development of a 5 MW reference gearbox for offshore wind turbines: 5 MW reference gearbox

    SciTech Connect

    Nejad, Amir Rasekhi; Guo, Yi; Gao, Zhen; Moan, Torgeir

    2015-07-27

    This paper presents detailed descriptions, modeling parameters and technical data of a 5MW high-speed gearbox developed for the National Renewable Energy Laboratory offshore 5MW baseline wind turbine. The main aim of this paper is to support the concept studies and research for large offshore wind turbines by providing a baseline gearbox model with detailed modeling parameters. This baseline gearbox follows the most conventional design types of those used in wind turbines. It is based on the four-point supports: two main bearings and two torque arms. The gearbox consists of three stages: two planetary and one parallel stage gears. The gear ratios among the stages are calculated in a way to obtain the minimum gearbox weight. The gearbox components are designed and selected based on the offshore wind turbine design codes and validated by comparison to the data available from large offshore wind turbine prototypes. All parameters required to establish the dynamic model of the gearbox are then provided. Moreover, a maintenance map indicating components with high to low probability of failure is shown. The 5 MW reference gearbox can be used as a baseline for research on wind turbine gearboxes and comparison studies. It can also be employed in global analysis tools to represent a more realistic model of a gearbox in a coupled analysis.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. The 1.5 MW wind turbine of tomorrow

    SciTech Connect

    De Wolff, T.J.; Sondergaard, H.

    1996-12-31

    The Danish company Nordtank is one of the pioneers within the wind turbine industry. Since 1981 Nordtank has installed worldwide more than 2300 wind turbine generators with a total name plate capacity that is exceeding 350 MW. This paper will describe two major wind turbine technology developments that Nordtank has accomplished during the last year: Site Optimization of Nordtank wind turbines: Nordtank has developed a flexible design concept for its WTGs in the 500/600 kW range, in order to offer the optimal WTG solution for any given site and wind regime. Nordtank`s 1.5 MW wind turbine: In September 1995, Nordtank was the first company to install a commercial 1.5 NM WTG. This paper will document the development process, the design as well as operations of the Nordtank 1.5 MW WTG.

  13. 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.

  14. 1.5 MW RF Load for ITER

    SciTech Connect

    Ives, Robert Lawrence; Marsden, David; Collins, George; Karimov, Rasul; Mizuhara, Max; Neilson, Jeffrey

    2016-09-01

    Calabazas Creek Research, Inc. developed a 1.5 MW RF load for the ITER fusion research facility currently under construction in France. This program leveraged technology developed in two previous SBIR programs that successfully developed high power RF loads for fusion research applications. This program specifically focused on modifications required by revised technical performance, materials, and assembly specification for ITER. This program implemented an innovative approach to actively distribute the RF power inside the load to avoid excessive heating or arcing associated with constructive interference. The new design implemented materials and assembly changes required to meet specifications. Critical components were built and successfully tested during the program.

  15. 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.

  16. 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.

  17. 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

  18. 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.

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

    SciTech Connect

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

    1995-12-31

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

  20. 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.

  1. Development of 1 to 1.5 MW CW Gyrotrons

    NASA Astrophysics Data System (ADS)

    Felch, K.; Blank, M.; Borchard, P.; Cahalan, P.; Cauffman, S.; Chu, S.; Jory, H.

    2003-10-01

    High power mm-wave sources provide electron cyclotron heating, current drive, and instability suppression in fusion plasmas. CPI has delivered three 110 GHz, 1 MW gyrotrons for ECH and ECCD experiments on DIII-D, each of which has demonstrated reliable operation at 1 MW for pulse lengths up to 5 seconds. CPI has also delivered a 140 GHz, 1 MW gyrotron to IPP for use on W-7X. This gyrotron has produced a peak output power of 900 kW, and pulse lengths up to 700 seconds at 500 kW. Ten consecutive 500 kW 600 second pulses were demonstrated without fault at 25CPI's test facilities could not support long pulse operation at full power, such operation is planned at IPP. The 140 GHz system employs a diode magnetron injection gun, a TE_28,7 cavity interaction mode, an internal mode converter to produce a Gaussian output beam, a low-loss CVD diamond output window, and a single-stage depressed-voltage beam collector to enhance the overall electrical efficiency of the device. Currently, under a DOE development program, CPI is fabricating a 110 GHz, 1.3-1.5 MW CW depressed-collector gyrotron to deliver improved reliability at power levels above 1 MW.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  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. 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).

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. JPRS Report Science & Technology China: Energy 5MW Low Power Reactor

    DTIC Science & Technology

    2007-11-02

    monocrystalline silicon neutron irradiation doping, molybdenum- technetium isotope production, irradia- tion coloring of gemstones, and so on. Key terms: 5MW low...power reactor, unloaded fuel ele- ments, element damage monitoring, irradiation, monoc- rystalline silicon, molybdenum- technetium isotopes. I...comprehensive use of the LPR, and undertake monocrystalline silicon neutron irradiation doping, molybdenum- technetium isotope production, irradiation color

  1. 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.

  2. 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).

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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%.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

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

    SciTech Connect

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

    2008-12-16

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

  19. 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.

  20. Raft River 5MW Power Plant: a small binary power plant

    SciTech Connect

    Whitbeck, J.F.; DiBello, E.G.; Walrath, L.F.

    1982-01-01

    The Raft River 5MW power plant is a binary cycle pilot plant. The system uses isobutane in a dual boiling cycle. This cycle was selected because the well field and temperatures were not well known at the time of cycle selection, and therefore, a boiling cycle was desirable. The dual boiling feature provides about 15 to 20% more power and makes the output less sensitive to changes in geothermal temperature changes than a single boiler system. The plant design was based upon a 290F geothermal fluid temperature at the inlet to the plant and has a gross nominal generator rating of 5MW; however, actual output will vary according to ambient wet bulb temperatures over a range from 4.4MW to 6.2MW with the actual plant inlet temperature of 278F being obtained. The plant is supplied by three production wells. Geothermal fluid boost pumps within the plant inlet provide the pressure necessary to overcome plant pressure drop and return the fluid to the two injection sites. All long runs of the buried geothermal piping external to the plant boundaries use cement-asbestos pipe. The physical size and manpower requirements for the Raft River facility, the economics of small plant operation, and operational experience are discussed.

  1. Internal Technical Report, Safety Analysis Report 5 MW(e) Raft River Pilot Plant

    SciTech Connect

    Brown, E.S.; Homer, G.B.; Spencer, S.G.; Shaber, C.R.

    1980-05-30

    The Raft River Geothermal Site is located in Southern Idaho's Raft River Valley, southwest of Malta, Idaho, in Cassia County. EG and G idaho, Inc., is the DOE's prime contractor for development of the Raft River geothermal field. Contract work has been progressing for several years towards creating a fully integrated utilization of geothermal water. Developmental progress has resulted in the drilling of seven major DOE wells. Four are producing geothermal water from reservoir temperatures measured to approximately 149 C (approximately 300 F). Closed-in well head pressures range from 69 to 102 kPa (100 to 175 psi). Two wells are scheduled for geothermal cold 60 C (140 F) water reinjection. The prime development effort is for a power plant designed to generate electricity using the heat from the geothermal hot water. The plant is designated as the ''5 MW(e) Raft River Research and Development Plant'' project. General site management assigned to EG and G has resulted in planning and development of many parts of the 5 MW program. Support and development activities have included: (1) engineering design, procurement, and construction support; (2) fluid supply and injection facilities, their study, and control; (3) development and installation of transfer piping systems for geothermal water collection and disposal by injection; and (4) heat exchanger fouling tests.

  2. Internal Technical Report, Safety Analysis Report 5 MW(e) Raft River Research and Development Plant

    SciTech Connect

    Brown, E.S.; Homer, G.B.; Shaber, C.R.; Thurow, T.L.

    1981-11-17

    The Raft River Geothermal Site is located in Southern Idaho's Raft River Valley, southwest of Malta, Idaho, in Cassia County. EG and G idaho, Inc., is the DOE's prime contractor for development of the Raft River geothermal field. Contract work has been progressing for several years towards creating a fully integrated utilization of geothermal water. Developmental progress has resulted in the drilling of seven major DOE wells. Four are producing geothermal water from reservoir temperatures measured to approximately 149 C (approximately 300 F). Closed-in well head pressures range from 69 to 102 kPa (100 to 175 psi). Two wells are scheduled for geothermal cold 60 C (140 F) water reinjection. The prime development effort is for a power plant designed to generate electricity using the heat from the geothermal hot water. The plant is designated as the ''5 MW(e) Raft River Research and Development Plant'' project. General site management assigned to EG and G has resulted in planning and development of many parts of the 5 MW program. Support and development activities have included: (1) engineering design, procurement, and construction support; (2) fluid supply and injection facilities, their study, and control; (3) development and installation of transfer piping systems for geothermal water collection and disposal by injection; and (4) heat exchanger fouling tests.

  3. 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.

  4. 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.

  5. Deevelopment of a 1.5 MW, 140 GHz coaxial gyrotron

    SciTech Connect

    Piosczyk, B.; Dammertz, G.; Iatrou, C.T.; Moebius, A.; Zhang, S.C.

    1995-12-31

    A 1.5 MW, 140 GHz, TE{sub 28,16}-coaxial gyrotron with an inverse MIG is under development. Preliminary rf-tests using an axial rf output and a simple cavity with a constant diameter and non-corrugated inner rod gave an rf output power of 1 MW with an efficiency of 23% at 140 GHz (TE{sub 28,16}) and 1.3 MW with an efficiency of 29% at 133 GHz (TE{sup 27,15}). No indications of beam instabilities in the beam tunnel between the IMIG gun and the cavity have been observed. Experiments with an improved cavity and the design of the tube with a radial dual Gaussian beam output and a depressed collector are underway.

  6. Development of a 1.5 MW coaxial gyrotron at 165 GHz

    SciTech Connect

    Iatrou, C.T.; Dammertz, G.; Piosczyk, B.; Zhang, S.C.

    1995-12-31

    The development of a 165 GHz - 1.5 MW coaxial cavity gyrotron operating in the TE{sub 31,17} mode is presented. The selection of the operating frequency and mode are based on the limitations imposed by the maximum field of the existing SC magnet at FZK, the use of the inverse MIG of the 140 GHz-TE{sub 28,16} coaxial gyrotron, and the possibility of transforming the operating mode to a whispering gallery mode (WGM), appropriate for the dual-beam q.o. output coupler and the two output rf windows. The cavity with a tapered and longitudinally corrugated inner rod, the nonlinear uptaper and a new rf window are under construction. First experiments with an axial output tube are foreseen in November 1995.

  7. Definition of a 5MW/61.5m wind turbine blade reference model.

    SciTech Connect

    Resor, Brian Ray

    2013-04-01

    A basic structural concept of the blade design that is associated with the frequently utilized %E2%80%9CNREL offshore 5-MW baseline wind turbine%E2%80%9D is needed for studies involving blade structural design and blade structural design tools. The blade structural design documented in this report represents a concept that meets basic design criteria set forth by IEC standards for the onshore turbine. The design documented in this report is not a fully vetted blade design which is ready for manufacture. The intent of the structural concept described by this report is to provide a good starting point for more detailed and targeted investigations such as blade design optimization, blade design tool verification, blade materials and structures investigations, and blade design standards evaluation. This report documents the information used to create the current model as well as the analyses used to verify that the blade structural performance meets reasonable blade design criteria.

  8. Design of Electron Gun for 1.5 MW, 140 GHz Gyrotron

    NASA Astrophysics Data System (ADS)

    Singh, Udaybir; Kumar, Nitin; Purohit, L. P.; Sinha, A. K.

    2011-02-01

    This paper presents the design of the triode type electron gun for a 140 GHz, 1.5 MW gyrotron with the transverse to the axial velocity ratio of the beam 1.4 and the transverse velocity spread 1.28%. The operating mode of the gyrotron is TE24,8 and it is operated in the fundamental harmonic. The analytic trade-off equations for the electron gun design have been used to estimate the initial gun parameters. The electron trajectory tracing program has been used to optimize the electron gun design. The parametric dependences of modulating anode voltage, beam voltage and cathode magnetic field on the beam quality has also been studied.

  9. 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.

  10. 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.

  11. Statistical fault diagnosis of wind turbine drivetrain applied to a 5MW floating wind turbine

    NASA Astrophysics Data System (ADS)

    Ghane, Mahdi; Nejad, Amir R.; Blanke, Mogens; Gao, Zhen; Moan, Torgeir

    2016-09-01

    Deployment of large scale wind turbine parks, in particular offshore, requires well organized operation and maintenance strategies to make it as competitive as the classical electric power stations. It is important to ensure systems are safe, profitable, and cost-effective. In this regards, the ability to detect, isolate, estimate, and prognose faults plays an important role. One of the critical wind turbine components is the gearbox. Failures in the gearbox are costly both due to the cost of the gearbox itself and also due to high repair downtime. In order to detect faults as fast as possible to prevent them to develop into failure, statistical change detection is used in this paper. The Cumulative Sum Method (CUSUM) is employed to detect possible defects in the downwind main bearing. A high fidelity gearbox model on a 5-MW spar-type wind turbine is used to generate data for fault-free and faulty conditions of the bearing at the rated wind speed and the associated wave condition. Acceleration measurements are utilized to find residuals used to indirectly detect damages in the bearing. Residuals are found to be nonGaussian, following a t-distribution with multivariable characteristic parameters. The results in this paper show how the diagnostic scheme can detect change with desired false alarm and detection probabilities.

  12. Target designs for the Brookhaven National Laboratory 5-MW pulsed spallation neutron source

    SciTech Connect

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

    1996-03-01

    A feasibility study of a compact high power density target for a spallation neutron source was under-taken. The target arrangement consists primarily of heavy metal, with appropriate cooling passages. A high intensity proton beam of intermediate energy is directed at the target, where it interacts with the heavy metal nuclei. The subsequent spallation reactions produce several neutrons per proton resulting in an intense neutron source. The proton beam is assumed to havean energy of 5 MW, and to be cyclic with a repetition rate of 10Hz and 50Hz. The study was divided into two broad sections. First, an analysis of preliminary target designs was undertaken to ensure the overall feasibility of the concepts involved in the design and eventual construction of such a high power density target. Second, two proposed target designs, based on the first set of analyses, are investigated in more detail. Special care is taken to ensure that the neutron fluxes in the moderator are at the desired level no material compatibility problems exist,and the target is able to operate in a reliable and safe manner. Several target materials, coolant types, and target arrangements are investigated in the first section. The second section concentrates on a single target material and geometric arrangement. However, several structural material choices continue to be investigated with the aim of minimizing the effects of structural heating, and associated thermally induced stresses. In the final section the conclusions of this preliminary study are summarized.

  13. Fluid-structure coupled computations of the NREL 5MW wind turbine blade during standstill

    NASA Astrophysics Data System (ADS)

    Dose, B.; Rahimi, H.; Herráez, I.; Stoevesandt, B.; Peinke, J.

    2016-09-01

    This work is aimed at investigating the aero-elastic behavior of a wind turbine blade subjected to strong wind speeds during standstill. This type of investigation still remains a challenge for most wind turbine simulation codes. For this purpose, a new developed high fidelity framework for fluid-structure coupled computations of wind turbines is presented and numerical simulations are conducted on the NREL 5MW reference wind turbine. The framework couples the open-source Computational Fluid Dynamics (CFD) toolbox OpenFOAM with an in-house beam solver, based on the Geometrically Exact Beam Theory (GEBT). The obtained results are compared to the aero-elastic tool FAST, which is based on the Blade Element Momentum theory (BEM) and can be considered as a state-of-the-art wind turbine simulation code. The evaluation of the fluid-structure coupled CFD simulations reveals clear differences in the results compared to FAST. While the mean deflections show a reasonable agreement, the dynamics of the edgewise deflections differ significantly. Furthermore, the effect of an explicit coupling versus an implicit coupling strategy on the results is investigated.

  14. Neutronic analysis of the conversion of HEU to LEU fuel for a 5-MW MTR core

    SciTech Connect

    Pazirandeh, A.; Bartsch, G.

    1987-01-01

    In recent years, due to cessation of highly enriched uranium (HEU) fuel supply, practical steps have been taken to substitute HEU fuel in almost all research reactors by medium-enriched uranium or low-enriched uranium (LEU) fuels. In this study, a neutronic calculation of a 5-MW research reactor core fueled with HEU (93% /sup 235/U) is presented. In order to assess the performance of the core with the LEU (< 20%) fuel replacement, while keeping fuel element geometry nearly unchanged, several different /sup 235/U loadings were examined. The core consists of 22 standard fuel elements (SFEs) and 6 control fuel elements (CFEs). Each fuel elements has 18 curved plates of which two end plates are dummies. Initial /sup 235/U content is 195 g /sup 235/U/SFE and 9.7 g /sup 235/U/CFE or /PFE. In all calculations the permitted changes to the fuel elements are (a) 18 active plates per SFE, (b) fuel plates assumed to be flat, and (c) 8 or 9 active plates per CFE.

  15. Testing of an Advanced Internal Mode Converter for a 1.5 MW, 110 GHz Gyrotron

    NASA Astrophysics Data System (ADS)

    Tax, D. S.; Mastovsky, I.; Neilson, J.; Shapiro, M. A.; Sirigiri, J. R.; Temkin, R. J.; Torrezan, A. C.

    2009-11-01

    Megawatt gyrotrons are under development for the electron cyclotron heating (ECH) of plasmas, including ITER. To optimize the efficiency of gyrotrons and of the transmission lines, the internal mode converter (IMC) should output a perfect Gaussian beam. The TE22,6 110 GHz IMC we have implemented consists of a helically-cut launcher and three smooth curved mirrors. The theoretically predicted output beam has waist Wz = Wx = 2.9 cm at the gyrotron window. Cold test measurements using a VNA and a 3-axis scanner were in good agreement with theory with measured beam waists Wz = 2.9 cm and Wx = 2.7 cm. We also installed the IMC in a 110 GHz, 1.5 MW, 3 μs pulsed gyrotron and measured the field pattern with over 40 dB signal to noise accuracy using an rf diode on a 2-axis scanner. Measured beam waists Wz = 4.8 cm and Wx = 4.2 cm compared well with theoretical waists Wz = Wx = 4.7 cm at a plane 124 cm from the gyrotron window.

  16. Experimental Research on a 1.5 MW, 110 GHz Gyrotron

    NASA Astrophysics Data System (ADS)

    Shapiro, M. A.; Hidaka, Y.; Choi, E. M.; Mastovsky, I.; Sirigiri, J. R.; Tax, D. S.; Temkin, R. J.; Neilson, J.

    2008-11-01

    We report experimental research on the after cavity interaction (ACI) in a 1.5-MW, 110-GHz gyrotron with an internal mode converter operating in 3 microsecond pulses. Recent experiments with a single-stage depressed collector revealed the effects of the ACI, a second interaction that occurs after the electron beam passes through the intended primary interaction region. The ACI causes re-absorption of the microwave power and broadening of the spent electron beam energy distribution, thus leading to a significant reduction in gyrotron efficiency. The broadening of the spent electron beam energy spectrum, which results in degraded performance of the depressed collector, has been experimentally verified. Ways to minimize the ACI are currently being investigated. Also, a new internal mode converter, consisting of a helically-cut launcher and four smooth curved mirrors, has been designed and fabricated. The cold test shows a good agreement with the theoretical Gaussian beam pattern. This new converter will be hot tested shortly in the gyrotron.

  17. 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.

  18. 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.

  19. A 10-GeV, 5-MW proton source for a pulsed spallation source

    SciTech Connect

    Cho, Y.; Chae, Y.C.; Crosbie, E.

    1995-12-31

    A feasibility study for a pulsed spallation source based on a 5-MW, 10-GeV rapid proton synchrotron (RCS) is in progress. The integrated concept and performance parameters of the facility are discussed. The 10-GeV synchrotron uses as its injector the 2-GeV accelerator system of a 1-MW source described elsewhere. The 1-MW source accelerator system consists of a 400-MeV H{sup {minus}} linac with 2.5 MeV energy spread in the 75% chopped (25% removed) beam and a 30-Hz RCS that accelerates the 400-MeV beam to 2 GeV. The time averaged current of the accelerator system is 0.5 mA, equivalent to 1.04 {times} 10{sup 14} protons per pulse. The 10-GeV RCS accepts the 2 GeV beam and accelerates it to 10 GeV. Beam transfer from the 2-GeV synchrotron to the 10-GeV machine u highly efficient bunch-to-bucket injection, so that the transfer can be made without beam loss. The synchrotron lattice uses FODO cells of 90{degrees} phase advance. Dispersion-free straight sections are obtained using a missing magnet scheme. The synchrotron magnets are powered by dual-frequency resonant circuits. The magnets are excited at a 20-Hz rate and de-excited at 60-Hz. resulting in an effective 30-Hz rate. A key feature of the design of this accelerator system is that beam losses are minimized from injection to extraction, reducing activation to levels consistent with hands-on maintenance. Details of the study are presented.

  20. 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.

  1. 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.

  2. 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.

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

    PubMed

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  5. 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.

  6. Short-pulse MOPA fiber laser with kilowatt average power and multi-megawatt peak power, applying advanced XLMA fiber amplifiers

    NASA Astrophysics Data System (ADS)

    Dinger, R.; Grundmann, F.-P.; Hapke, C.; Kallage, P.; Rath, W.; Ruppik, S.

    2017-03-01

    High power short pulse fiber lasers are applied in industry for many ablation processes or various surface treatments, and there is a huge demand for such lasers but with higher average power, higher pulse energy and higher peak power. This contribution presents a high peak- and average- power fiber laser with selectable pulse durations between 10 ns and 100 ns, where more than 150 mJ pulse energy has been achieved at a repetition rate of 10 kHz. In addition, for a laser pulse with 30 ns pulse duration a maximum peak power of more than 3.5 MW at more than 1 kW average output power have been demonstrated. These results could be achieved by applying extra-large mode area (XLMA) gain fibers (fiber core <100 μm) in the fiber amplifiers and using pulse shape capabilities of the seed laser, only. Stable and safe operation of the fiber laser have been shown with power densities up to 3 GW/cm² in the gain fiber. In order to protect the fiber laser to be affected by back reflections from the workpiece, a newly designed optical isolator with more than 30 dB isolation has been implemented.

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

    NASA Astrophysics Data System (ADS)

    Roth, Markus

    2011-09-01

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

  8. 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.

  9. Internal Technical Report, Software Requirements and Design Guide for the 5MW(e) Raft River Pilot Plant

    SciTech Connect

    Metcalf, D.D.; Cole, M.S.

    1980-05-15

    The 5MW(e) electrical generating plant is a demonstrational unit intended to provide engineering data basic to improvement of geothermal-electric technology. It is anticipated that the plant will operate on a production basis after initial testing, and that periodic re-testing will be done to measure the effects of fouling in heat exchanges and aging generally. The initial tests will confirm engineering estimates of performance, and will identify optimum feasible operatinq conditions and maximum power generating capacity. They will also identify any anomalous plant behavior not foreseen. Several tests will lead to quantification of constant and variable terms used in thermodynamic relationships descriptive of plant and subsystem behavior. Because the product of the testing will be confirmatory engineering data heretofore unavailable, the plant has been carefully instrumented, with either explicit or implicit instrumentation redundancy for most parameters to be measured. The 5MW(e) data system collects the data directly from the instrumentation. Enhancements such as on-line analytical routines may be added later, but initially, data capture shall be the sole activity of the data system. The 5MW(e) plant converts the energy of geothermally heated water to electrical energy conforming to 60 Hz commercial power standards. The plant capacity is sufficiently large to be useful in a demonstrational sense, but is limited to a capacity conservative of the geothermal energy resource, which hasn't been fully explored. The 5MW(e) plant will continue on a regular production basis after completion of the testing. Additional production units may be added at a later time.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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)].

  1. 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.

  2. 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.

  3. 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.

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

    SciTech Connect

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

    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.

  5. 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.

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

    SciTech Connect

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

    2014-07-07

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

  7. 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.

  8. 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.

  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. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Interaction of Atmospheric Turbulence with Blade Boundary Layer Dynamics on a 5MW Wind Turbine using Blade-Boundary-Layer-Resolved CFD with hybrid URANS-LES.

    SciTech Connect

    Vijayakumar, Ganesh; Brasseur, James; Lavely, Adam; Jayaraman, Balaji; Craven, Brent

    2016-01-04

    We describe the response of the NREL 5 MW wind turbine blade boundary layer to the passage of atmospheric turbulence using blade-boundary-layer-resolved computational fluid dynamics with hybrid URANS-LES modeling.

  16. 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.

  17. 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.

  18. 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)

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

    PubMed

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

    2016-02-12

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

  20. 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)

  1. 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.

  2. 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.

  3. 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

  4. Heat accumulation in ultra-short pulsed scanning laser ablation of metals.

    PubMed

    Bauer, Franziska; Michalowski, Andreas; Kiedrowski, Thomas; Nolte, Stefan

    2015-01-26

    High average laser powers can have a serious adverse impact on the ablation quality in ultra-short pulsed laser material processing of metals. With respect to the scanning speed, a sharp transition between a smooth, reflective and an uneven, dark ablated surface is observed. Investigating the influence of the sample temperature, it is experimentally shown that this effect stems from heat accumulation. In a numerical heat flow simulation, the critical scanning speed indicating the change in ablation quality is determined in good agreement with the experimental data.

  5. Silicon nanoparticle formation by short pulse electrochemical etching in the transition regime

    NASA Astrophysics Data System (ADS)

    Nychyporuk, T.; Lysenko, V.; Gautier, B.; Barbier, D.

    2006-11-01

    Controlled formation of a monolayer or doublelayer of laterally separated Si nanoparticles at the surface of Si wafers with the use of short pulse anodization in the transition regime is reported and compared with two other anodization regimes: nanopore formation and electropolishing. The initial stages of the dynamics of the nanoparticle formation are studied in detail by means of atomic force microscopy. Detailed structural analysis of the height and surface density of the nanoparticles with respect to anodization current density, electrolyte composition, and anodization time has been performed.

  6. Dynamics of atomic spin-orbit-state wave packets produced by short-pulse laser photodetachment

    NASA Astrophysics Data System (ADS)

    Law, S. M. K.; Gribakin, G. F.

    2016-11-01

    We analyze the experiment by Hultgren et al. [Phys. Rev. A 87, 031404 (2013), 10.1103/PhysRevA.87.031404] on orbital alignment and quantum beats in coherently excited atomic fine-structure manifolds produced by short-pulse laser photodetachment of C-,Si-,and Ge- negative ions, and derive a formula that describes the beats. Analysis of the experimental data enables us to extract the noncoherent background contribution for each species, and indicates the need for a full density-matrix treatment of the problem.

  7. Electron Dynamics During High-Power, Short-Pulsed Laser Interactions with Solids and Interfaces

    DTIC Science & Technology

    2016-06-28

    AFRL-AFOSR-VA-TR-2016-0234 Electron Dynamics During High-Power, Short-Pulsed Laser Interactions with Solids and Interfaces Patrick Hopkins...1. REPORT DATE (DD-MM-YYYY) 28-05-2016 2. REPORT TYPE Final 3. DATES COVERED (From - To) 01-02-2013 - 31-01-2016 4. TITLE AND SUBTITLE Electron ...PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Patrick E. Hopkins 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND

  8. Dynamometer Testing of Samsung 2.5MW Drivetrain: Cooperative Research and Development Final Report, CRADA Number CRD-08-311

    SciTech Connect

    Wallen, R.

    2011-02-01

    SHI's prototype 2.5 MW wind turbine drivetrain was tested at the NWTC 2.5 MW dynamometer test facility over the course of 4 months between December 2009 and March 2010. This successful testing campaign allowed SHI to validate performance, safety, control tuning, and reliability in a controlled environment before moving to full-scale testing and subsequent introduction of a commercial product into the American market.

  9. Natural snowfall reveals large-scale flow structures in the wake of a 2.5-MW wind turbine.

    PubMed

    Hong, Jiarong; Toloui, Mostafa; Chamorro, Leonardo P; Guala, Michele; Howard, Kevin; Riley, Sean; Tucker, James; Sotiropoulos, Fotis

    2014-06-24

    To improve power production and structural reliability of wind turbines, there is a pressing need to understand how turbines interact with the atmospheric boundary layer. However, experimental techniques capable of quantifying or even qualitatively visualizing the large-scale turbulent flow structures around full-scale turbines do not exist today. Here we use snowflakes from a winter snowstorm as flow tracers to obtain velocity fields downwind of a 2.5-MW wind turbine in a sampling area of ~36 × 36 m(2). The spatial and temporal resolutions of the measurements are sufficiently high to quantify the evolution of blade-generated coherent motions, such as the tip and trailing sheet vortices, identify their instability mechanisms and correlate them with turbine operation, control and performance. Our experiment provides an unprecedented in situ characterization of flow structures around utility-scale turbines, and yields significant insights into the Reynolds number similarity issues presented in wind energy applications.

  10. RBF neural network based PI pitch controller for a class of 5-MW wind turbines using particle swarm optimization algorithm.

    PubMed

    Poultangari, Iman; Shahnazi, Reza; Sheikhan, Mansour

    2012-09-01

    In order to control the pitch angle of blades in wind turbines, commonly the proportional and integral (PI) controller due to its simplicity and industrial usability is employed. The neural networks and evolutionary algorithms are tools that provide a suitable ground to determine the optimal PI gains. In this paper, a radial basis function (RBF) neural network based PI controller is proposed for collective pitch control (CPC) of a 5-MW wind turbine. In order to provide an optimal dataset to train the RBF neural network, particle swarm optimization (PSO) evolutionary algorithm is used. The proposed method does not need the complexities, nonlinearities and uncertainties of the system under control. The simulation results show that the proposed controller has satisfactory performance.

  11. Short-pulse Calorimetric Load for High Power Millimeter-wave Beams

    NASA Astrophysics Data System (ADS)

    Gandini, F.; Bruschi, A.; Cirant, S.; Gittini, G.; Granucci, G.; Muzzini, V.; Sozzi, C.; Spinicchia, N.

    2007-02-01

    A spherical compact matched load, for high vacuum operation suited for short pulses (2 MW, 0.1 s) precise measurement has been designed to test high power gyrotrons Bruschi, Gandini, Muzzini, Spinicchia, Cirant, Gittini, Granucci, Mellera, Nardone, Simonetto, and Sozzi (Fusion Eng. Des. 56 57:649 654, 2001); Bruschi, Cirant, Gandini, Granucci, Mellera, Muzzini, Nardone, Simonetto, Sozzi, and Spinicchia (Nucl. Fusion 43:1513 1519, 2003); Bruschi, Cirant, Gandini, Gittini, Granucci, Mellera, Muzzini, Nardone, Simonetto, Sozzi, Spinicchia, Angella, and Signorelli (Development of CW and short-pulse calorimetric loads for high power millimeter-wave Beams, 23rd Symposium on Fusion Technology, September 20 24, 2004, Venice, Italy). In order to enhance the power handling capability of the load and to reduce the operation problems that may arise from an excessive reflection from the load, a ray tracing code has been written to model the power distribution on the inner surface and the pattern of the reflected radiation. The outcome of this code has been used to select a more convenient profile for the spreading mirror of the load and to optimize a pre-load specially conceived to minimize the power reflected fraction.

  12. Transient thermal and nonthermal electron and phonon relaxation after short-pulsed laser heating of metals

    SciTech Connect

    Giri, Ashutosh; Hopkins, Patrick E.

    2015-12-07

    Several dynamic thermal and nonthermal scattering processes affect ultrafast heat transfer in metals after short-pulsed laser heating. Even with decades of measurements of electron-phonon relaxation, the role of thermal vs. nonthermal electron and phonon scattering on overall electron energy transfer to the phonons remains unclear. In this work, we derive an analytical expression for the electron-phonon coupling factor in a metal that includes contributions from equilibrium and nonequilibrium distributions of electrons. While the contribution from the nonthermal electrons to electron-phonon coupling is non-negligible, the increase in the electron relaxation rates with increasing laser fluence measured by thermoreflectance techniques cannot be accounted for by only considering electron-phonon relaxations. We conclude that electron-electron scattering along with electron-phonon scattering have to be considered simultaneously to correctly predict the transient nature of electron relaxation during and after short-pulsed heating of metals at elevated electron temperatures. Furthermore, for high electron temperature perturbations achieved at high absorbed laser fluences, we show good agreement between our model, which accounts for d-band excitations, and previous experimental data. Our model can be extended to other free electron metals with the knowledge of the density of states of electrons in the metals and considering electronic excitations from non-Fermi surface states.

  13. 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.

  14. Resonant third-harmonic generation of a short-pulse laser from electron-hole plasmas

    SciTech Connect

    Kant, Niti; Nandan Gupta, Devki; Suk, Hyyong

    2012-01-15

    In semiconductors, free carriers are created in pairs in inter-band transitions and consist of an electron and its corresponding hole. At very high carrier densities, carrier-carrier collisions dominate over carrier-lattice collisions and carriers begin to behave collectively to form plasma. Here, we apply a short-pulse laser to generate third-harmonic radiation from a semiconductor plasma (electron-hole plasma) in the presence of a transverse wiggler magnetic-field. The process of third-harmonic generation of an intense short-pulse laser is resonantly enhanced by the magnetic wiggler, i.e., wiggler magnetic field provides the necessary momentum to third-harmonic photons. In addition, a high-power laser radiation, propagating through a semiconductor imparts an oscillatory velocity to the electrons and exerts a ponderomotive force on electrons at the third-harmonic frequency of the laser. This oscillatory velocity produces a third-harmonic longitudinal current. And due to the beating of the longitudinal electron velocity and the wiggler magnetic field, a transverse third-harmonic current is produced that drives third-harmonic electromagnetic radiation. It is finally observed that for a specific wiggler wave number value, the phase-matching conditions for the process are satisfied, leading to resonant enhancement in the energy conversion efficiency.

  15. 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.

  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. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. The implementation and data analysis of an interferometer for intense short pulse laser experiments

    SciTech Connect

    Park, Jaebum; Baldis, Hector A.; Chen, Hui

    2016-01-01

    We present an interferometry setup and the detailed fringe analysis method for intense short pulse (SP) laser experiments. The interferometry scheme was refined through multiple campaigns to investigate the effects of pre-plasmas on energetic electrons at the Jupiter Laser Facility at Lawrence Livermore National Laboratory. The interferometer used a frequency doubled (${\\it\\lambda}=0.527~{\\rm\\mu}\\text{m}$) 0.5 ps long optical probe beam to measure the pre-plasma density, an invaluable parameter to better understand how varying pre-plasma conditions affect the characteristics of the energetic electrons. The hardware of the diagnostic, data analysis and example data are presented. The diagnostic setup and the analysis procedure can be employed for any other SP laser experiments and interferograms, respectively.

  3. 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.

  4. Modeling of Dense Plasma Effects in Short-Pulse Laser Experiments

    NASA Astrophysics Data System (ADS)

    Walton, Timothy; Golovkin, Igor; Macfarlane, Joseph; Prism Computational Sciences, Madison, WI Team

    2016-10-01

    Warm and Hot Dense Matter produced in short-pulse laser experiments can be studied with new high resolving power x-ray spectrometers. Data interpretation implies accurate modeling of the early-time heating dynamics and the radiation conditions that are generated. Producing synthetic spectra requires a model that describes the major physical processes that occur inside the target, including the hot-electron generation and relaxation phases and the effect of target heating. An important issue concerns the sensitivity of the predicted K-line shifts to the continuum lowering model that is used. We will present a set of PrismSPECT spectroscopic simulations using various continuum lowering models: Hummer/Mihalas, Stewart-Pyatt, and Ecker-Kroll and discuss their effect on the formation of K-shell features. We will also discuss recently implemented models for dense plasma shifts for H-like, He-like and neutral systems.

  5. 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.

  6. Monte Carlo simulation of wave sensing with a short pulse radar

    NASA Technical Reports Server (NTRS)

    Levine, D. M.; Davisson, L. D.; Kutz, R. L.

    1977-01-01

    A Monte Carlo simulation is used to study the ocean wave sensing potential of a radar which scatters short pulses at small off-nadir angles. In the simulation, realizations of a random surface are created commensurate with an assigned probability density and power spectrum. Then the signal scattered back to the radar is computed for each realization using a physical optics analysis which takes wavefront curvature and finite radar-to-surface distance into account. In the case of a Pierson-Moskowitz spectrum and a normally distributed surface, reasonable assumptions for a fully developed sea, it has been found that the cumulative distribution of time intervals between peaks in the scattered power provides a measure of surface roughness. This observation is supported by experiments.

  7. 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.

  8. 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.

  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. 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.

  11. Short-pulsed laser transport in two-dimensional scattering media by natural element method.

    PubMed

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

    2014-04-01

    The natural element method (NEM) is extended to solve transient radiative transfer (TRT) in two-dimensional semitransparent media subjected to a collimated short laser irradiation. The least-squares (LS) weighted residuals approach is employed to spatially discretize the transient radiative heat transfer equation. First, for the case of the refractive index matched boundary, LSNEM solutions to TRT are validated by comparison with results reported in the literature. Effects of the incident angle on time-resolved signals of transmittance and reflectance are investigated. Afterward, the accuracy of this algorithm for the case of the refractive index mismatched boundary is studied. Finally, the LSNEM is extended to study the TRT in a two-dimensional semitransparent medium with refractive index discontinuity irradiated by the short pulse laser. The effects of scattering albedo, optical thickness, scattering phase function, and refractive index on transmittance and reflectance signals are investigated. Several interesting trends on the time-resolved signals are observed and analyzed.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Integrable multi-component generalization of a modified short pulse equation

    NASA Astrophysics Data System (ADS)

    Matsuno, Yoshimasa

    2016-11-01

    We propose a multi-component generalization of the modified short pulse (SP) equation which was derived recently as a reduction of Feng's two-component SP equation. Above all, we address the two-component system in depth. We obtain the Lax pair, an infinite number of conservation laws and multisoliton solutions for the system, demonstrating its integrability. Subsequently, we show that the two-component system exhibits cusp solitons and breathers for which the detailed analysis is performed. Specifically, we explore the interaction process of two cusp solitons and derive the formula for the phase shift. While cusp solitons are singular solutions, smooth breather solutions are shown to exist, provided that the parameters characterizing the solutions satisfy certain conditions. Last, we discuss the relation between the proposed system and existing two-component SP equations.

  17. 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.

  18. 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.

  19. 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}.

  20. 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.

  1. Osteoblast behavior on various ultra short pulsed laser deposited surface coatings.

    PubMed

    Qu, Chengjuan; Myllymaa, Sami; Prittinen, Juha; Koistinen, Arto P; Lappalainen, Reijo; Lammi, Mikko J

    2013-04-01

    Ultra short pulsed laser deposition technique was utilized to create amorphous diamond, alumina and carbon nitride, and two different titania coatings on silicon wafers, thus producing five different surface deposited films with variable physico-chemical properties. The surface characterizations, including the roughness, the contact angle and the zeta potential measurements were performed before we tested the growth properties of human osteoblast-like Saos-2 cells on these surfaces (three separate experiments). The average roughness and hydrophobicity were the highest on titania-deposited surfaces, while carbon nitride was the most hydrophilic one. Osteoblasts on all surfaces showed a flattened, spread-out morphology, although on amorphous diamond the cell shape appeared more elongated than on the other surfaces. On rough titania, the area covered by the osteoblasts was smaller than on the other ones. Cell proliferation assay did not show any statistically significant differences. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. 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.

  3. 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

  4. 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.

  5. Process Properties of Electronic High Voltage Discharges Triggered by Ultra-short Pulsed Laser Filaments

    NASA Astrophysics Data System (ADS)

    Cvecek, Kristian; Gröschel, Benjamin; Schmidt, Michael

    Remote processing of metallic workpieces by techniques based on electric arc discharge or laser irradiation for joining or cutting has a long tradition and is still being intensively investigated in present-day research. In applications that require high power processing, both approaches exhibit certain advantages and disadvantages that make them specific for a given task. While several hybrid approaches exist that try to combine the benefits of both techniques, none were as successful in providing a fixed electric discharge direction as discharges triggered by plasma filaments generated by ultra-short pulsed lasers. In this work we investigate spatial and temporal aspects of laser filament guided discharges and give an upper time delay between the filament creation and the electrical build-up of a dischargeable voltage for a successful filament triggered discharge.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Two-dimensional electromagnetic Child-Langmuir law of a short-pulse electron flow

    SciTech Connect

    Chen, S. H.; Tai, L. C.; Liu, Y. L.; Ang, L. K.; Koh, W. S.

    2011-02-15

    Two-dimensional electromagnetic particle-in-cell simulations were performed to study the effect of the displacement current and the self-magnetic field on the space charge limited current density or the Child-Langmuir law of a short-pulse electron flow with a propagation distance of {zeta} and an emitting width of W from the classical regime to the relativistic regime. Numerical scaling of the two-dimensional electromagnetic Child-Langmuir law was constructed and it scales with ({zeta}/W) and ({zeta}/W){sup 2} at the classical and relativistic regimes, respectively. Our findings reveal that the displacement current can considerably enhance the space charge limited current density as compared to the well-known two-dimensional electrostatic Child-Langmuir law even at the classical regime.

  11. 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.

  12. Optical coherence tomography in material deformation by using short pulse laser irradiation

    NASA Astrophysics Data System (ADS)

    Choi, Eun Seo; Kwak, Wooseop; Shin, Yongjin; Kim, Youngseop; Jung, Woonggyu; Ahn, Yeh-Chan; Chen, Zhongping; Jeong, Eun Joo; Kim, Chang-Seok

    2008-02-01

    We demonstrate the feasibility of OCT imaging for the investigation of samples, which are processed by the short pulse laser. The use of short pulse lasers in various material processing have provided the advantages such as a high peak power and a small heat affected zone over conventional methods based on mechanical treatment. However, due to the improper application of the lasers, the unwanted surface or structural deformation of materials and the thermal damages around an irradiation spot can be caused. Thus, the real-time monitoring/evaluation of laser processing performance in-situ is needed to prevent the excessive deformation of the material and to determine optimal processing conditions. As a standard method to investigation of the material processing by using the lasers, the scanning electron microscopy (SEM) or the transmission electron microscopy (TEM) observation of a physically cleaved surface is used although sample damages are given during the cleaving and polishing process. In this paper, we utilized the OCT advantages such as high resolution and non-invasive investigation to evaluate the laser processing performance. OCT images for the deformation monitoring of the ABS plastic present correlation with images obtained from conventional investigation methods. OCT images of the maxillary bone clearly show the difference in the pit formation of the biological sample at different irradiation conditions. We prove the potential of OCT for the evaluation of laser-processed various samples. Integrating OCT system into a laser processing system, we can visualize the effect of laser-based treatments in clinical and industrial fields.

  13. 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.

  14. 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

  15. Monitoring a 5 MW offshore wind energy converter—Condition parameters and triangulation based extraction of modal parameters

    NASA Astrophysics Data System (ADS)

    Häckell, Moritz W.; Rolfes, Raimund

    2013-10-01

    The test field alpha ventus is the first operating German offshore parks for wind energy. Twelve Wind Energy Converters (WECs) of the 5 MW-class are installed, both, for commercial and research reasons. Due to upcoming mass production and uncertainties in loads and behaviour, monitoring the foundation of these structures was desired. Two goals addressed are the extraction of modal parameters for model validation and the estimation of condition parameters to allow a hypothesis of the system's state. In a first step the largedatabase is classified by Environmental and Operational Conditions (EOCs) through affinity propagation which is a new approach for Structural Health Monitoring (SHM) on wind turbines. Further, system identification through data driven stochastic subspace identification (SSI) is performed. A new, automated approach called triangulation-based extraction of modal parapeters (TEMP), using stability diagrams, is a key focus of the presented research. Finally, extraction of condition parameters for tower accelerations classified by EOCs, based on covariance driven SSI and Vector Auto-Regressive (VAR) Models, is performed for several observation periods from one to 16 weeks. These parameters and their distributions provide a base line for long term observations.

  16. Investigations for Improvement of Energy Yield of Rotor-blades from the 1.5 MW Class

    NASA Astrophysics Data System (ADS)

    Balaresque, N.; Bicker, S.; Dollinger, C.; Fandrich, A.; Gatz, S.; Hölling, M.; Irschik, K.; Reichstein, T.; Schaffarczyk, A. P.; von Zengen, C.

    2016-09-01

    In a combined approach of extensive measurement and accompanying simulation a wind turbine blade used in the 1.5 MW class was investigated for improvement of aerodynamic properties and especially the energy yield. One blade was dismantled and its geometry was locally measured by a specially designed laser scanning-system. From this geometry data set five 2D wind tunnel models were manufactured and measured in the wind tunnel of Deutsche Wind Guard Engineering GmbH at Bremerhaven, Germany. In addition, extensive CFD investigations were performed to investigate the usefulness of so-called aerodynamic devices like vortex generators, Gurney flaps and others for improving energy yield. As a result it could be shown that the aerodynamic efficiency of the manufactured blades - if measured in terms of lift-to-drag ratio - is at a high level but still can be further improved. 3D CFD investigations were able to show the influence of Gurney flaps and boundary layer fences and their interactions.

  17. Fatigue loading on a 5MW offshore wind turbine due to the combined action of waves and current

    NASA Astrophysics Data System (ADS)

    Peeringa, Johan M.

    2014-06-01

    In the design of an offshore wind turbine the natural frequencies of the structure are of importance. In the design of fixed offshore wind turbine support structures it cannot be avoided that the first eigenmode of the structure lies in the frequency band of wave excitation. This study indicates that wave-current interaction should be taken into account for support structure design load calculations. Wave-current interaction changes the shape of the wave spectrum and the energy content in the wave frequency range of 0.2 - 0.35Hz. This is in the range of natural frequencies fixed offshore wind turbine structures are designed for. The waves are affected by the current in two ways. First there is a frequency shift, Doppler effect, for the fixed observer when the wave travels on a current. Second the shape of the wave is modified in case the wave travels from an area without current into an area with current. Due to wave-current interaction the wave height and wave length change. For waves on an opposing current the wave energy content increases, while for wave on a following current the wave energy content slightly reduces. Simulations of normal production cases between cut-in and cut-out wind speed are performed for a 5MW wind turbine in 20m water depth including waves with 1) a following current, 2) an opposing current and 3) no current present. In case of waves having an opposing current, the 1Hz equivalent fore-aft tower bending moment at the seabed is about 10% higher compared to load cases with waves only.

  18. New insights on the interaction between atmospheric flow and a full-scale 2.5 MW wind turbine

    NASA Astrophysics Data System (ADS)

    Chamorro, L. P.; Lee, S.; Olsen, D.; Milliren, C.; Marr, J.; Arndt, R.; Sotiropoulos, F.

    2012-12-01

    Power fluctuations and fatigue loads are among the most significant problems that wind turbines face throughout their lifetime. Atmospheric turbulence is the common driving mechanism that triggers instabilities on these quantities. Reducing the effects of the fluctuating flow on wind turbines is quite challenging due to the wide variety of length scales present in the boundary layer flow. Each group of these scales, which range from the order of a millimeter to kilometer and larger, plays a characteristic and distinctive role on the performance and structural reliability of wind turbines. This study seeks to contribute toward the understanding on the complex scale-to-scale interaction between wind turbine and flow turbulence. Novel insights into the physical mechanisms that govern the flow/turbine interaction will be discussed. To tackle the problem, we investigate the unsteady behavior of a full-scale 2.5 MW wind turbine under nearly neutral thermal stratification. The study is performed in the Eolos Wind Energy Research Field Station of the University of Minnesota. An instrumented 130 meter meteorological tower located upstream of a Clipper Liberty C96 wind turbine is used to characterize the turbulent flow and atmospheric conditions right upstream of the wind turbine. High resolution and synchronous measurements of the approach wind velocity at several heights, turbine power and strain at the tower foundation are used to determine the scale-to-scale interaction between flow and the wind turbine performance and its physical structure. The spectral distribution of the fluctuating turbine power and instantaneous stresses will be discussed in detail. Characteristic length scales playing a key role on the dynamics of the wind turbine as well as the distinctive effects of flow coherent motions and strong intermittent gusts will also be addressed. Funding was provided by the U.S. Department of Energy (DE-EE0002980) and Xcel Energy through the Renewable Development Fund

  19. 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

  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. Analysis of temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system

    NASA Astrophysics Data System (ADS)

    Zhu, Ping; Xie, Xinglong; Zhu, Jianqiang; Zhu, Haidong; Yang, Qingwei; Kang, Jun; Guo, Ailin; Gao, Qi

    2014-11-01

    In extremely intense laser system used for plasma physics experiments, temporal contrast is an important property of the ultra-short pulse. In this paper, we theoretically study the temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system. Two-step focusing fast Fourier transform (FFT) algorithm with the coordinate transform based on Fresnel approximation in space domain and Fourier integral transform method in time domain were used to simulate the focusing process spatially and temporally, in which the spatial distribution of ultra-short pulse temporal contrast characteristics at the focal spot is related to the wave front in large aperture off-axis parabolic mirror focusing optical system. Firstly, temporal contrast degradation due to wave front noise with higher spatial frequency is analyzed and appropriate evaluation parameter for large aperture ultra-short pulse focusing system is put forward from the perspective of temporal contrast. Secondly, the influence of wave front distortion with lower spatial frequency on temporal contrast is revealed comparing different degradation characteristics of various aberrations. At last, a method by controlling and optimizing the wave front to prevent temporal contrast degradation in large aperture ultra-short laser system is proposed, which is of great significance for high temporal contrast petawatt laser facilities.

  4. 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.

  5. Chitinolytic Streptomyces vinaceusdrappus S5MW2 isolated from Chilika lake, India enhances plant growth and biocontrol efficacy through chitin supplementation against Rhizoctonia solani.

    PubMed

    Yandigeri, Mahesh S; Malviya, Nityanand; Solanki, Manoj Kumar; Shrivastava, Pooja; Sivakumar, G

    2015-08-01

    A chitinolytic actinomycete Streptomyces vinaceusdrappus S5MW2 was isolated from water sample of Chilika lake, India and identified using 16S rRNA gene sequencing. It showed in vitro antifungal activity against the sclerotia producing pathogen Rhizoctonia solani in a dual culture assay and by chitinase enzyme production in a chitin supplemented minimal broth. Moreover, isolate S5MW2 was further characterized for biocontrol (BC) and plant growth promoting features in a greenhouse experiment with or without colloidal chitin (CC). Results of greenhouse experiment showed that CC supplementation with S5MW2 showed a significant growth of tomato plants and superior disease reduction as compared to untreated control and without CC treated plants. Moreover, higher accumulation of chitinase also recovered in the CC supplemented plants. Significant effect of CC also concurred with the Analysis of Variance of greenhouse parameters. These results show that the a marine antagonist S5MW2 has BC efficiency against R. solani and chitinase enzyme played important role in plant resistance.

  6. Resistance and recovery of river biofilms receiving short pulses of Triclosan and Diuron.

    PubMed

    Proia, L; Morin, S; Peipoch, M; Romaní, A M; Sabater, S

    2011-08-01

    The effects of the herbicide Diuron (DIU) and the bactericide Triclosan (TCS) were assessed on laboratory-grown stream biofilms. Four week-old biofilms were exposed in mesocosms to 48-hours of short pulses of either DIU or TCS. The direct and indirect effects of each toxicant on the biofilms, and the subsequent recovery of the biofilms, were evaluated according to structural and functional biomarkers. These parameters were analyzed immediately before exposure, immediately after exposure, and 9 and 16days post-exposure. DIU caused an increase in diatom mortality (+79%), which persisted until the end of the experiment. TCS also affected diatom mortality (+41%), although the effect did not appear until 1week post-exposure. TCS caused an increase in bacterial mortality (+45%); however, this parameter returned to normal values 1week post-exposure. TCS compromised the cellular integrity of the green alga Spirogyra sp., whereas DIU did not. TCS also strongly inhibited phosphate uptake (-71%), which did not return to normal values until 2weeks post-exposure. DIU directly affected algae, but barely affected the heterotrophs, whereas TCS seriously impaired bacteria (direct effect) as well as autotrophs (indirect effect). However, the biofilms recovered their normal structure and function within only a few days to a few weeks. These findings demonstrate the capacity of biofilms to cope with periodic inputs of toxicants, but also the risks associated to repeated exposure or multi-contamination in aquatic ecosystems. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Theoretical analysis of saturation and limit cycles in short pulse FEL oscillators

    SciTech Connect

    Piovella, N.; Chaix, P.; Jaroszynski, D.

    1995-12-31

    We derive a model for the non linear evolution of a short pulse oscillator from low signal up to saturation in the small gain regime. This system is controlled by only two independent parameters: cavity detuning and losses. Using a closure relation, this model reduces to a closed set of 5 non linear partial differential equations for the EM field and moments of the electron distribution. An analysis of the linearised system allows to define and calculate the eigenmodes characterising the small signal regime. An arbitrary solution of the complete nonlinear system can then be expanded in terms of these eigenmodes. This allows interpreting various observed nonlinear behaviours, including steady state saturation, limit cycles, and transition to chaos. The single mode approximation reduces to a Landau-Ginzburg equation. It allows to obtain gain, nonlinear frequency shift, and efficiency as functions of cavity detuning and cavity losses. A generalisation to two modes allows to obtain a simple description of the limit cycle behaviour, as a competition between these two modes. An analysis of the transitions to more complex dynamics is also given. Finally, the analytical results are compared to the experimental data from the FELIX experiment.

  8. 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

  9. Large Area and Short Pulsed Shock Initiation of A TATB/HMX Mixed Explosive

    NASA Astrophysics Data System (ADS)

    Wang, Guiji; Sun, Chengwei; Chen, Jun; Liu, Cangli; Tan, Fuli; Zhang, Ning

    2007-06-01

    The large area and short pulsed shock initiation experiment on a plastic bonded mixed explosive of TATB(80%) and HMX(15%) has been performed with an electric gun where a mylar flyer of 19mm in diameter and 0.05˜0.30mm in thickness is launched by an electrically exploding metallic bridge foil. The cylindrical explosive specimens (φ16mm x 8mm in size) were initiated by the mylar flyers in thickness of 0.07˜0.20mm, which induced shock pressure in specimen was of duration ranging 0.029˜0.109μs. The experimental data were treated with the DRM(Delayed Robbins-Monro) procedure and to provide the threshold of shock pressure P 13.73˜5.23GPa. The shock initiation criterion of the explosive specimen is (P/GPa)^1.451(τ/μs) = 1.2. Meanwhile the criterion in 100% probability in the experiment is (P/GPa)^1.8(τ/μs) = 2.63. In addition, the 30^o wedged specimen was tested and the shock to detonation transition (SDT) process emerging on its inclined surface was diagnosed with a device consisting of multiple optical fiber probe, optoelectronic transducer and digital oscilloscope. The POP plot of the explosive has been gained from above SDT data.

  10. Large Area and Short-Pulse Shock Initiation of a Tatb/hmx Mixed Explosive

    NASA Astrophysics Data System (ADS)

    Guiji, Wang; Chengwei, Sun; Jun, Chen; Cangli, Liu; Jianheng, Zhao; Fuli, Tan; Ning, Zhang

    2007-12-01

    The large area and short-pulse shock initiation experiments on the plastic bonded mixed explosive of TATB(80%) and HMX(15%) have been performed with an electric gun where a Mylar flyer of 10-19 mm in diameter and 0.05˜0.30 mm in thickness was launched by an electrically exploding metallic bridge foil. The cylindrical explosive specimens (Φ16 mm×8 mm in size) were initiated by the Mylar flyers in thickness of 0.07˜0.20 mm, which induced shock pressure in specimen was of duration ranging from 0.029 to 0.109 μs. The experimental data were treated with the DRM(Delayed Robbins-Monro) procedure and to provide the initiation threshold of flyer velocities at 50% probability are 3.398˜1.713 km/s and that of shock pressure P 13.73˜5.23 GPa, respectively for different pulse durations. The shock initiation criteria of the explosive specimen at 50% and 100% probabilities are yielded. In addition, the 30° wedged sample was tested and the shock to detonation transition (SDT) process emerging on its inclined surface was diagnosed with a device consisting of multiple optical fiber probe, optoelectronic transducer and digital oscilloscope. The POP plot of the explosive has been gained from above SDT data.

  11. Multi-phase ionization dynamics of carbon thin film irradiated by high power short pulse laser

    NASA Astrophysics Data System (ADS)

    Kawahito, Daiki; Kishimoto, Yasuaki

    2017-10-01

    The ionization dynamics of a carbon thin film irradiated by a high power short pulse laser in the range of 1019-20 W/cm2 are studied using the extended particle-based integrated code (EPIC), which includes atomic and collisional processes. Two types of ionization dynamics exhibiting different spatio-temporal structures are found to predominantly regulate the process, and arise depending on the laser amplitude. The first is a fast convective propagation for charge states up to C4+, which keeps a steep ionization front. The velocity of the front is of the order of the speed of light. The front formation results from the localized longitudinal electrostatic field and associated field ionization, which in turn propagates inside the film. This convective propagation is triggered when the laser field becomes high enough that electron bunches accelerated by the laser ponderomotive force reach relativistic energies and penetrate inside the film across the surface. The second dynamics is a fast non-diffusive propagation of ionization showing a long plasma density scale length for C5+ and C6+. This process results predominantly from electron impact ionization by high energy electron bunches successively produced by the laser. These electron bunches also excite wake fields that propagate inside the film and contribute to ionizing the film to higher charge states, i.e., C5+ and C6+, especially near the front surface. The effect of field ionization loss, which sensitively influences the ionization dynamics in the relatively low laser power regime, is also discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  13. 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.

  14. 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.

  15. Investigation of energy partitioning from Leopard short-pulse laser interactions in mass limited targets

    NASA Astrophysics Data System (ADS)

    Griffin, B.; Sawada, H.; Yabuuchi, T.; McLean, H.; Patel, P.; Beg, F.

    2013-10-01

    The energy distribution in the interaction of a high-intensity, short-pulse laser with a mass limited target was investigated by simultaneously collecting x-ray and particle data. The Leopard laser system at the Nevada Terawatt Facility delivered 15 J of energy in a 350 fs pulse duration. With a beam spot size limited to within 8 μm, the target interaction achieved a peak intensity of 1019 W/cm2 at 20° incidence. The size of the Cu foil targets was varied from 2-20 μm in thickness and from 50 by 50 μm to 2000 by 2000 μm in surface area. A Bragg crystal x-ray spectrometer and a spherical crystal imager were used to measure 7.5-9.5 keV x-rays and 8.05 keV monochromatic x-ray images respectively. The escaping electrons and protons in the rear were monitored with a magnet-based electron spectrometer and radiochromic film. Preliminary results show both a decrease of the K β/K α ratio and a stronger He α emission for smaller sized targets, less than 250 by 250 μm. The detailed analyses of the K α images and particle data will be presented.

  16. Calibration and Characterization of Single Photon Counting Cameras for Short-Pulse Laser Experiments

    SciTech Connect

    Maddox, B R; Park, H; Remington, B A; McKernan, M

    2008-05-05

    The photon counting efficiency of various CCD based cameras was studied as a function of x-ray energy and exposure. A pair of Spectral Instruments Model 800 CCD cameras fitted with 16 {micro}m thick back-illuminated CCDs were calibrated at low x-ray energy using two well established histogram methods, a standard pixel for pixel histogram and the single pixel event histogram method. In addition, two new thick substrate CCDs were evaluated for use at high energy. One was a commercially available Princeton Instruments LCX1300 deep depletion CCD camera while the other was a custom designed 650 {micro}m thick partially depleted CCD fitted to a SI 800 camera body. It is shown that at high x-ray energy, only a pixel-summing algorithm was able to derive spectral data due to the spreading of x-ray events over many pixels in the thicker substrate CCDs. This paper will describe the different algorithms used to extract spectra and the absolute detection efficiencies using these algorithms. These detectors will be very useful to detect high-energy x-ray photons from high-intensity short pulse laser interactions.

  17. 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.

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  1. Four-wave mixing and generation of short pulses in multimode class B laser amplifiers

    NASA Astrophysics Data System (ADS)

    Jahanpanah, J.; Moradi, H.

    2013-04-01

    The linear and nonlinear amplification features of an optical signal by a multimode class B laser have been discussed. The four-wave mixing process between the cavity central mode and the amplified input signal produces a sequence of satellite lines. It is demonstrated that short pulses can be formed by phase beating the satellite lines. In the linear regime, the laser amplifier acts like a three-mode free-running laser where the oscillations of two right and left adjacent modes are substituted by those of the amplified input signal and its image satellite line. In the nonlinear regime, two more symmetrical adjacent satellite lines are first added to the cavity electric field components and then the frequency of the cavity central mode is shifted towards the image satellite lines. At the same time, the number of central-mode photons is gradually decreased by raising the input signal strength. The central-mode photons are ultimately reduced to zero, where an injection-locking phenomenon takes place. Finally, we derive a heuristic conservation relation between the input energies to the laser by sum of the pumping and injected signals, and those distributed between the signal and image satellite lines and spontaneous emission radiation.

  2. 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.

  3. 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.

  4. Invited paper: Short pulse generation in mid-IR fiber lasers

    NASA Astrophysics Data System (ADS)

    Hudson, Darren D.

    2014-12-01

    Mode-locked fiber lasers emitting short pulses of light at wavelengths of 2 μm and longer are reviewed. Rare-earth doped silica and fluoride fiber lasers operating in the mode-locked regime in the mid-IR (2-5 μm) have attracted attention due to their usefulness to spectroscopy, nonlinear optics, laser surgery, remote sensing and ranging to name a few. While silica fiber lasers are fundamentally limited to emission wavelengths below 2.2 μm, fluoride fiber lasers can reach to nearly 4 μm. The relative infancy of fluoride fibers as compared to silica fibers means the field has work to do to translate the mode-locking techniques to systems beyond 2 μm. However, with the recent demonstration of a stable, mode-locked 3 μm fiber laser, the possibility of achieving high performance 3 μm class mode-locked fiber lasers looks promising.

  5. Calibration and characterization of single photon counting cameras for short-pulse laser experiments.

    PubMed

    Maddox, B R; Park, H S; Remington, B A; McKernan, M

    2008-10-01

    The x-ray photon counting efficiency of various charged-coupled device (CCD) based cameras was studied as a function of photon energy and exposure. A pair of Spectral Instruments model 800 CCD cameras fitted with 16 microm thick back-illuminated CCDs were calibrated at low x-ray energy using two well established histogram methods. In addition, two new thick substrate CCDs were evaluated for use at high energy. One was a commercially available Princeton Instruments PI-LCX1300 deep depletion CCD camera, while the other used a custom designed 650 microm thick partially depleted CCD fitted to a Spectral Instruments model 800 camera body. It is shown that at high x-ray energy, a pixel-summing algorithm is necessary to reconstruct the x-ray spectra in the thicker substrate CCDs. This paper will describe the different algorithms used to extract spectra and the absolute detection efficiencies using these algorithms. These detectors and algorithms will be very useful in detecting high-energy x-ray photons from high-intensity short-pulse laser interactions.

  6. Short-pulse excimer laser performances and its applications: I. ophthamology

    NASA Astrophysics Data System (ADS)

    Przybylski, Marius; Simon, Gabriel

    1997-05-01

    A new very small powerful air-cooled excimer laser (193, 248, 308 nm) with metal-ceramic technology was developed by ATL Lasertechnik in Germany. The laser won 1995 Prize for the best innovation awarded by German federal states of Berlin & Brandenburg. The pulse energy of 10 - 20 mJ at high rep rates (200 - 500 Hz) from an active volume of only 1 cm3 are reached. The raw laser beam produces energy density of > 100 mJ/cm2 which is comparable to the performance of standard (large) excimer lasers. Its very short pulse length (3 ns), permits extremely high peak power density (30 MW/cm2). The ATLEX SP laser uses a new type of pre-ionization technique providing high beam homogeneity at low discharge voltages. Small footprint and weight, low operation costs opens up new industrial (micro-machining) and biomedical applications. Recently the ATLEX SP laser (193 nm) has been used for corneal refractive surgery. The setup consists of splitting a 193 nm laser beam into couples of beams which simultaneously ablates the corneal surface in a symmetrical scan-like fashion. Refractive changes up to 20 diopters were realized. Results of an analysis by corneal topography showed homogeneous ablation throughout the entire ablation zone.

  7. Exploring polygon scanner head capabilities for ultra-short pulse laser texturing

    NASA Astrophysics Data System (ADS)

    Mincuzzi, G.; Fleureau, M.; Faucon, M.; Kling, R.

    2016-03-01

    The combination of both, fast beam scanning systems and high repetition rate, high average power lasers, represents an interesting technological solution for surface texturing by Ultra-Short Pulses Laser to gain a foothold into industrial environment for commercial purposes. Nevertheless unwanted thermal effects are expected when the average power exceeds some tens of W. An interesting strategy for a reliable heat management would consists of texturing surfaces with a low fluence values (slightly higher than the ablation threshold) and utilising a polygon scanning head which is able to deflect the laser beam with unprecedented speed. Here we show that over stainless steel, it is possible to obtain different surface textures (in particular ripples, micro grooves and spikes) by utilising a 2 MHz femtosecond laser jointly with a fast and accurate polygonal scanner head at relatively low fluence (0.11 J·cm-2). The evolution of the Laser induced surface structures morphology is shown when varying the scan speed between 25 m·s-1 and 90 m·s-1. Two different wavelengths have been utilised for the process λ= 1030 nm and λ = 515 nm and the difference of the results obtained have been highlighted. Moreover, a full structures morphology characterization by SEM has been carried out for all the textured surfaces. Finally, by increasing the number of successive surface scans is possible to tailor the surface reflectivity. As a result an average reflectivity value of < 5% over the visible range has been extracted from a blackened stainless steel surface.

  8. Creation of Pure Frozen Gas Targets for Ion Acceleration using Short Pulse Lasers

    NASA Astrophysics Data System (ADS)

    McCary, Edward; Stehr, Florian; Jiao, Xuejing; Quevedo, Hernan; Franke, Philip; Agustsson, Ronald; Oshea, Finn; Berry, Robert; Chao, Dennis; Woods, Kayley; Gautier, Donald; Letzring, Sam; Hegelich, Bjorn

    2015-11-01

    A system for shooting interchangeable frozen gas targets was developed at the University of Texas and will be tested at Los Alamos National Lab. A target holder which can hold up to five substrates used for target growing was cryogenically cooled to temperatures below 14 K. The target substrates consist of holes with diameters ranging from 15 μm-500 μm and TEM grids with micron scale spacing, across which films of ice are frozen by releasing small amounts of pure gas molecules directly into the vacuum target chamber. Frozen gas targets comprised of simple molecules like methane and single element gasses like hydrogen and deuterium will provide novel target configuations that will be compared with laser plasma interaction simulations. The targets will be shot with the ultra-intense short-pulse Trident laser. Accelerated ion spectra will be characterized using a Thomson Parabola with magnetic field strength of 0.92T and electric field strength of 30kV. Hydrogen targets will be additionally characterized using stacks of copper which become activated upon exposure to energetic protons resulting in a beta decay signal which be imaged on electron sensitive imaging plates to provide an energy spectrum and spacial profile of the proton beam. Details of target creation and pre-shot characterization will be presented.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. Method of synchronization measurement via spatial-spectral interference in coherent combination of multi-channel ultra-short pulses

    NASA Astrophysics Data System (ADS)

    Li, Z. L.; Zuo, Y. L.; Wu, Z. H.; Wang, X.; Mu, J.; Yu, H. Y.; Zhao, D.; Zhu, Q. H.; Su, J. Q.; Zhou, K. N.; Zhou, S.; Feng, X.; Zhang, S.; Liu, H. Z.

    2017-08-01

    Spatial-spectral interference fringes contain information on the time delay between pulses. By extracting the slope of the equiphase line in the spatial-spectral interference fringes, a large range and high-precision detection of the time delay is realized. Theoretical analysis is given. An experiment demonstrates the fundamental process for obtaining the time delay between two femtosecond pulses. In the current experiment the measurement range is from 0.4 fs to hundreds of fs. This method was first proposed for synchronization measurement of coherent combination of ultra-short pulses in a multi-channel system. The method can be applied at large scales in an ultra-short pulse laser facility.

  2. 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.

  3. 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.

  4. Short-pulse Laser Induced Transient Structure Formation and Ablation Studied with Time-resolved Coherent XUV-scattering

    SciTech Connect

    Sokolowski-Tinten, Klaus; Shymanovich, Uladzimir; Barty, Anton; Chapman, Henry; Bajt, Sasa; Schulz, Joachim; Boutet, Sebastien; Bogan, Mike; Bostedt, Christoph; Marchesini, Stefano; Hau-Riege, Stefan; Frank, Matthias; Stojanovic, Nikola; Duesterer, Stefan; Redlin, Harald; Treusch, Rolf; Bonse, Joern; Rosandi, Yudi; Urbassek, Herbert M.; Tobey, Ra'anan

    2010-10-08

    The structural dynamics of short-pulse laser irradiated surfaces and nano-structures has been studied with nm spatial and ultrafast temporal resolution by means of single-shot coherent XUV-scattering techniques. The experiments allowed us to time-resolve the formation of laser-induced periodic surface structures, and to follow the expansion and disintegration of nano-objects during laser ablation.

  5. Modeling target bulk heating resulting from ultra-intense short pulse laser irradiation of solid density targets

    SciTech Connect

    Antici, P.; Gremillet, L.; Grismayer, T.; Audebert, P.; Mančic, A.; Fuchs, J.; Borghesi, M.; Cecchetti, C. A.

    2013-12-15

    Isochoric heating of solid-density matter up to a few tens of eV is of interest for investigating astrophysical or inertial fusion scenarios. Such ultra-fast heating can be achieved via the energy deposition of short-pulse laser generated electrons. Here, we report on experimental measurements of this process by means of time- and space-resolved optical interferometry. Our results are found in reasonable agreement with a simple numerical model of fast electron-induced heating.

  6. Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

    NASA Astrophysics Data System (ADS)

    Yuan, Y.; Greuner, H.; Böswirth, B.; Krieger, K.; Luo, G.-N.; Xu, H. Y.; Fu, B. Q.; Li, M.; Liu, W.

    2013-02-01

    Short pulse heat loads expected for vertical displacement events (VDEs) in ITER were applied in the high heat flux (HHF) test facility GLADIS at IPP-Garching onto samples of rolled W. Pulsed neutral beams with the central heat flux of 23 MW/m2 were applied for 0.5, 1.0 and 1.5 s, respectively. Rapid recrystallization of the adiabatically loaded 3 mm thick samples was observed when the pulse duration was up to 1.0 s. Grains grew markedly following recrystallization with increasing pulse length. The recrystallization temperature and temperature dependence of the recrystallized grain size were also investigated. The results showed that the recrystallization temperature of the W grade was around 2480 °C under the applied heat loading condition, which was nearly 1150 °C higher than the conventional recrystallization temperature, and the grains were much finer. A linear relationship between the logarithm of average grain size (ln d) and the inverse of maximum surface temperature (1/Tmax) was found and accordingly the activation energy for grain growth in temperature evolution up to Tmax in 1.5 s of the short pulse HHF load was deduced to be 4.1 eV. This provided an effective clue to predict the structure evolution under short pulse HHF loads.

  7. The short pulse carbon dioxide laser versus the colorado needle tip with electrocautery for upper and lower eyelid blepharoplasty.

    PubMed

    Rokhsar, Cameron K; Ciocon, David H; Detweiler, Susan; Fitzpatrick, Richard E

    2008-02-01

    Various techniques for blepharoplasty have been described, including those performed with the assistance of the short pulse carbon dioxide laser and those performed with the assistance of the Colorado microdissection needle attached to an electrocautery unit. Although the superiority of the carbon dioxide laser to cold steel has been demonstrated for the performance of eyelid blepharoplasty, no studies have ever compared the carbon dioxide laser to the Colorado needle. This is a paired comparison study in which 12 healthy patients underwent bilateral blepharoplasty of their upper and/or lower eyelids by a single surgeon. For each patient, a short pulse carbon dioxide laser was used on one side, and a Colorado needle attached to an electrocautery unit was used on the other. Intraoperative times were recorded. At five post-operative visits patients were evaluated for post-operative healing parameters including edema, erythema, scar width, and bruising. Finally, excised tissue was assessed histologically for thermal damage. Comparing both techniques, no difference in patient or physician-measured parameters of healing were noted up to 1 month post-operatively. However, Colorado needle assisted blepharoplasty resulted in slightly shorter intraoperative times. It also resulted in less thermal damage on a histologic level, although these differences were not clinically significant. For the performance of blepharoplasty, the Colorado needle tip with electrocautery offers benefits equivalent to those of the short pulsed CO2 laser but has the advantage of shorter intraoperative times and lower cost.

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

    SciTech Connect

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

    2007-10-01

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

  9. 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.

  10. 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

  11. Simulations of High-Intensity Short-Pulse Lasers Incident on Reduced Mass Targets

    NASA Astrophysics Data System (ADS)

    King, Frank W.

    This thesis presents the results of a series of fully kinetic particle-in-cell (PIC) simulations of reduced mass targets with pre-plasma subjected to high-intensity short-pulse lasers. The simulations are performed in one, two, and three dimensions. The results of these simulations show that the creation of an electrostatic collisionless ion shock in the preplasma controls the creation of an above solid density ion perturbation in the target bulk, and this determines the reduced mass target heating and deformation. The ion perturbation is initiated by a population of high-energy electrons that rapidly spread throughout the target and reflux. The perturbation spreads longitudinally and transversely through the target and results in compression followed by the destruction of the target. This deformation requires a kinetic treatment due to the generation of non-equilibrium particle distributions and the role of ballistic electrons and ions. Kinetic and fluid simulations are compared and both exhibit the basic features of the above solid density ion perturbation, but the magnitude of the effect and the speed of propagation vary significantly between the two methods. Kinetic simulations do not naturally include equation-of-state physics and other aspects of the problem. Both approaches are complementary. The requirements on spatial resolution, particle count, and other numerical parameters are addressed in this work. From these simulations, the behavior of the reduced mass targets is found to vary significantly depending on the laser focal spot size or the intensity of the laser pulse. This occurs even if the energy and power of the laser pulses are held constant. The number of dimensions used in the particle-in-cell simulations has been observed to have a significant effect on late-time heating of the target, but not during or shortly after laser excitation. This is due to the representation of the equilibration process as the initial population of laser heated

  12. Return current and proton emission from wire targets interacting with an intense short pulse laser

    NASA Astrophysics Data System (ADS)

    Beg, Farhat

    2004-05-01

    One of the important characteristics of short pulse high intensity laser-solid interactions is the generation of energetic charged particles, which result from the very efficient conversion of laser energy into hot electrons. Since the electrons in the electric field of the laser have relativistic quiver motions, the temperature of the hot electron distribution of the plasma produced at such extreme intensities can become very high. A large number of hot electrons (1013-1014) having an average energy of the order of 1-2 MeV can be generated as intensities exceed 1019 Wcm-2. Since the resulting beam current exceeds the Alfvén limit, a neutralizing return current of cold plasma electrons moving in the opposite direction is produced. Another source of return current is that due to the escape of very energetic electrons from the target, which then creates a large electrostatic potential due to charge separation. These return currents can cause significant ohmic heating. In addition escaping electrons establish the large electrostatic fields, accelerating a large number of protons from the target with energies of 10's of MeV. The experiments reported here were performed at the Rutherford Appleton Laboratory with the VULCAN laser facility at intensity greater than 5 x1019 Wcm-2 on wire targets. In some shots an additional wire or foil was placed nearby. The laser was blocked by the main wire target so that no laser light reached the additional wire or foil. Three main observations were made: (i) a Z-pinch was driven in the wire due to the return current, (ii) optical transition radiation (OTR) at 2w was generated and (iii) energetic proton emission was observed. The wire targets were observed to be ohmically heated and were m=0 unstable. The OTR emission is likely due to electron bunches accelerated by the ponderomotive force of the laser. The proton emission was in a form of thin disk perpendicular to the wire and centered on the wire at the laser focus. Proton

  13. 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

  14. Heat generation caused by ablation of dental restorative materials with an ultra short pulse laser (USPL) system

    NASA Astrophysics Data System (ADS)

    Braun, Andreas; Wehry, Richard; Brede, Olivier; Frentzen, Matthias; Schelle, Florian

    2011-03-01

    The aim of this study was to assess heat generation in dental restoration materials following laser ablation using an Ultra Short Pulse Laser (USPL) system. Specimens of phosphate cement (PC), ceramic (CE) and composite (C) were used. Ablation was performed with an Nd:YVO4 laser at 1064 nm and a pulse length of 8 ps. Heat generation during laser ablation depended on the thickness of the restoration material. A time delay for temperature increase was observed in the PC and C group. Employing the USPL system for removal of restorative materials, heat generation has to be considered.

  15. Drivetrain load effects in a 5-MW bottom-fixed wind turbine under blade-pitch fault condition and emergency shutdown

    NASA Astrophysics Data System (ADS)

    Rasekhi Nejad, Amir; Jiang, Zhiyu; Gao, Zhen; Moan, Torgeir

    2016-09-01

    In this paper, the effect of the blade-pitch fault and emergency shutdown on drivetrain responses in a 5-MW bottom-fixed wind turbine are investigated. A 5-MW reference gearbox with 4-point support is employed and the decoupled analysis approach is used for the load effect analysis. The effect of this fault event is then investigated for all bearings and gears inside the gearbox as well as main bearings. The results show that the blade-pitch fault creates significant axial forces on main bearings which increases the nontorque force entering the gearbox. Due to the emergency shutdown, the rotor torque reversal occurs which causes force reversals in gears. The main bearings are more affected than gears and bearings inside the gearbox in this fault condition and emergency shutdown, but first-stage bearings may also be considerably affected. It is therefore recommended to conduct a thorough inspection of main bearings and first stage bearings in case of such blade-pitch fault condition and emergency shutdown.

  16. 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.

  17. Determination of mean surface position and sea state from the radar return of a short-pulse satellite altimeter

    NASA Technical Reports Server (NTRS)

    Barrick, D. E.

    1972-01-01

    Using the specular point theory of scatter from a very rough surface, the average backscatter cross section per unit area per radar cell width is derived for a cell located at a given height above the mean sea surface. This result is then applied to predict the average radar cross section observed by a short-pulse altimeter as a function of time for two modes of operation: pulse-limited and beam-limited configurations. For a pulse-limited satellite altimeter, a family of curves is calculated showing the distortion of the leading edge of the receiver output signal as a function of sea state (i.e., wind speed). A signal processing scheme is discussed that permits an accurate determination of the mean surface position--even in high seas--and, as a by-product, the estimation of the significant seawave height (or wind speed above the surface). Comparison of these analytical results with experimental data for both pulse-limited and beam-limited operation lends credence to the model. Such a model should aid in the design of short-pulse altimeters for accurate determination of the geoid over the oceans, as well as for the use of such altimeters for orbital sea-state monitoring.

  18. Short-pulse Er:YAG laser increases bond strength of composite resin to sound and eroded dentin

    NASA Astrophysics Data System (ADS)

    Cersosimo, Maria Cecília Pereira; Matos, Adriana Bona; Couto, Roberta Souza D.'Almeida; Marques, Márcia Martins; de Freitas, Patricia Moreira

    2016-04-01

    This study evaluated the influence of the irradiation with a short-pulse Er:YAG laser on the adhesion of composite resin to sound and eroded dentin (SD and ED). Forty-six samples of occlusal dentine, obtained from human molars, had half of their surface protected, while the other half was submitted to erosive cycles. Afterward, 23 samples were irradiated with Er:YAG laser, resulting in four experimental groups: SD, sound irradiated dentine (SID-Er:YAG, 50 μs, 2 Hz, 80 mJ, and 12.6 J/cm2), ED, and eroded irradiated dentin (EID-erosion + Er:YAG laser). A self-etching adhesive system was used, and then cylinders of composite resin were prepared. A microshear bond strength test was performed after 24 h storage (n=20). The morphology of SD and ED, with or without Er:YAG laser irradiation, was evaluated under scanning electron microscopy (n=3). Bond strength values (MPa) were subjected to analysis of variance followed by Tukey's test. Statistically significant differences were found among the experimental groups: SD (9.76±3.39 B), SID (12.77±5.09 A), ED (5.12±1.72 D), and EID (7.62±3.39 C). Even though erosion reduces the adhesion to dentin, the surface irradiation with a short-pulse Er:YAG laser increases adhesion to both ED and SD.

  19. Temporal and spatial temperature distribution in the glabrous skin of rats induced by short-pulse CO2 laser

    NASA Astrophysics Data System (ADS)

    Lu, Pen-Li; Hsu, Shu-Shen; Tsai, Meng-Li; Jaw, Fu-Shan; Wang, An-Bang; Yen, Chen-Tung

    2012-11-01

    Pain is a natural alarm that aids the body in avoiding potential danger and can also present as an important indicator in clinics. Infrared laser-evoked potentials can be used as an objective index to evaluate nociception. In animal studies, a short-pulse laser is crucial because it completes the stimulation before escape behavior. The objective of the present study was to obtain the temporal and spatial temperature distributions in the skin caused by the irradiation of a short-pulse laser. A fast speed infrared camera was used to measure the surface temperature caused by a CO2 laser of different durations (25 and 35 ms) and power. The measured results were subsequently implemented with a three-layer finite element model to predict the subsurface temperature. We found that stratum corneum was crucial in the modeling of fast temperature response, and escape behaviors correlated with predictions of temperature at subsurface. Results indicated that the onset latency and duration of activated nociceptors must be carefully considered when interpreting physiological responses evoked by infrared irradiation.

  20. 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.

  1. Extreme states of matter in solids under short-pulse laser irradiation: a molecular-dynamics study

    NASA Astrophysics Data System (ADS)

    Lorazo, Patrick; Lewis, Laurent J.; Meunier, Michel

    2004-03-01

    The thermodynamic pathways through which a silicon target---initially in a hot, highly pressurized state---dilutes into vacuum as a result of short-pulse laser irradiation, are thoroughly investigated. This is accomplished by (1) using a combined molecular-dynamics and Monte Carlo approach to describe atom and carrier dynamics, respectively, and (2) following the thermodynamic evolution of the system during heating, expansion, and cooling [1]. Our results indicate a pulse duration upper limit for phase explosion in metals and semiconductors of ˜ 10-11s. For longer pulses, fragmentation, as originally proposed by Perez and Lewis for fs irradiation [1], remains the only relevant ablation mechanism [2]. Fragmentation can thus be viewed as the missing link in short-pulse laser ablation as it explains (1) the disappearance of Newton rings in the fs regime far from the ablation threshold, and (2) the matter removal dynamics with ``long''(> 10-11s) pulse durations. [1] D. Perez and L. J. Lewis, Phys. Rev. Lett. 89, 255504(2002); [2] P. Lorazo, L. J. Lewis, and M. Meunier, Phys. Rev. Lett. 91, 225502 (2003).

  2. Impact of Pre-Plasma on Fast Electron Generation and Transport from Short Pulse High Intensity Lasers

    NASA Astrophysics Data System (ADS)

    Peebles, J.; McGuffey, C.; Krauland, C.; Jarrott, L. C.; Sorokovikova, A.; Qiao, B.; Krasheninnikov, S.; Beg, F. N.; Wei, M. S.; Park, J.; Link, A.; Chen, H.; McLean, H. S.; Wagner, C.; Minello, V.; McCary, E.; Meadows, A.; Spinks, M.; Gaul, E.; Dyer, G.; Hegelich, B. M.; Martinez, M.; Donovan, M.; Ditmire, T.

    2014-10-01

    We present the results and analysis from recent short pulse laser matter experiments using the Texas Petawatt Laser to study the impact of pre-plasma on fast electron generation and transport. The experimental setup consisted of 3 separate beam elements: a main, high intensity, short pulse beam for the interaction, a secondary pulse of equal intensity interacting with a separate thin foil target to generate protons for side-on proton imaging and a third, low intensity, wider beam to generate a varied scale length pre-plasma. The main target consisted of a multilayer planar Al foil with a buried Cu fluor layer. The electron beam was characterized with multiple diagnostics, including several bremsstrahlung spectrometers, magnetic electron spectrometers and Cu-K α imaging. The protons from the secondary target were used to image the fields on the front of the target in the region of laser plasma interaction. Features seen in the interaction region by these protons will be presented along with characteristics of the generated electron beam. This work performed under the auspices of the US DOE under Contracts DE-FOA-0000583 (FES, NNSA).

  3. Vaporization and recondensation dynamics of indocyanine green-loaded perfluoropentane droplets irradiated by a short pulse laser

    NASA Astrophysics Data System (ADS)

    Yu, Jaesok; Chen, Xucai; Villanueva, Flordeliza S.; Kim, Kang

    2016-12-01

    Phase-transition droplets have been proposed as promising contrast agents for ultrasound and photoacoustic imaging. Short pulse laser activated perfluorocarbon-based droplets, especially when in a medium with a temperature below their boiling point, undergo phase changes of vaporization and recondensation in response to pulsed laser irradiation. Here, we report and discuss the vaporization and recondensation dynamics of perfluoropentane droplets containing indocyanine green in response to a short pulsed laser with optical and acoustic measurements. To investigate the effect of temperature on the vaporization process, an imaging chamber was mounted on a temperature-controlled water reservoir and then the vaporization event was recorded at 5 million frames per second via a high-speed camera. The high-speed movies show that most of the droplets within the laser beam area expanded rapidly as soon as they were exposed to the laser pulse and immediately recondensed within 1-2 μs. The vaporization/recondensation process was consistently reproduced in six consecutive laser pulses to the same area. As the temperature of the media was increased above the boiling point of the perfluoropentane, the droplets were less likely to recondense and remained in a gas phase after the first vaporization. These observations will help to clarify the underlying processes and eventually guide the design of repeatable phase-transition droplets as a photoacoustic imaging contrast agent.

  4. 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

  5. Using a short-pulse diffraction-limited laser beam to probe filamentation of a random phase plate smoothed beam.

    PubMed

    Kline, J L; Montgomery, D S; Flippo, K A; Johnson, R P; Rose, H A; Shimada, T; Williams, E A

    2008-10-01

    A short pulse (few picoseconds) laser probe provides high temporal resolution measurements to elucidate details of fast dynamic phenomena not observable with typical longer laser pulse probes and gated diagnostics. Such a short pulse laser probe (SPLP) has been used to measure filamentation of a random phase plate (RPP) smoothed laser beam in a gas-jet plasma. The plasma index of refraction due to driven density and temperature fluctuations by the RPP beam perturbs the phase front of a SPLP propagating at a 90 degree angle with respect to the RPP interaction beam. The density and temperature fluctuations are quasistatic on the time scale of the SPLP (approximately 2 ps). The transmitted near-field intensity distribution from the SPLP provides a measure of the phase front perturbation. At low plasma densities, the transmitted intensity pattern is asymmetric with striations across the entire probe beam in the direction of the RPP smoothed beam. As the plasma density increases, the striations break up into smaller sizes along the direction of the RPP beam propagation. The breakup of the intensity pattern is consistent with self-focusing of the RPP smoothed interaction beam. Simulations of the experiment using the wave propagation code, PF3D, are in qualitative agreement demonstrating that the asymmetric striations can be attributed to the RPP driven density fluctuations. Quantification of the beam breakup measured by the transmitted SPLP could lead to a new method for measuring self-focusing of lasers in underdense plasmas.

  6. Transformation of the frequency-modulated continuous-wave field into a train of short pulses by resonant filters

    NASA Astrophysics Data System (ADS)

    Shakhmuratov, R. N.

    2017-03-01

    The resonant filtering method transforming the frequency-modulated radiation field into a train of short pulses is proposed to be applied in the optical domain. Effective frequency modulation can be achieved by using an electro-optic modulator. Due to frequency modulation, a narrow-spectrum cw radiation field is seen by the resonant filter as a comb of equidistant spectral components separated by the modulation frequency. Tuning a narrow-bandwidth filter in resonance with the n th spectral component of the comb transforms the radiation field into bunches of pulses, with n pulses in each bunch. The transformation is explained by the interference of the coherently scattered resonant component of the field with the whole comb. Constructive interference results in the formation of pulses, while destructive interference is seen as dark windows between pulses. It is indicated that the optimal thickness of the resonant filter is several orders of magnitude smaller than the necessary thickness of the dispersive filters used before in the optical domain to produce short pulses from the frequency-modulated field.

  7. Numerical Analysis of NREL 5MW Wind Turbine: A Study Towards a Better Understanding of Wake Characteristic and Torque Generation Mechanism

    NASA Astrophysics Data System (ADS)

    Salman Siddiqui, M.; Rasheed, Adil; Tabib, Mandar; Kvamsdal, Trond

    2016-09-01

    With the increased feasibility of harvesting offshore wind energy, scale of wind turbines is growing rapidly and there is a trend towards clustering together higher number of turbines in order to harvest maximum yield and to leave a smaller footprint on the environment. This causes complex flow configurations inside the farms, the study of which is essential to making offshore wind energy a success. The present study focuses on NREL 5MW wind turbine with the following objectives (a)To compare Sliding Mesh Interface and Multiple Reference Frame modeling approaches and their predictive capabilities in reproducing the characteristics of flow around the full scale wind turbine. (b)To get a better insight into wake dynamics behind the turbine in near and far wake regions operating under different tip-speed-ratio and incoming turbulence intensities.

  8. Cooperation Reliability Testing of the Clipper Windpower Liberty 2.5 MW Turbine: Cooperative Research and Development Final Report, CRADA Number CRD-07-210

    SciTech Connect

    Hughes, S.

    2012-05-01

    Clipper Windpower (CWP) has developed the Liberty 2.5 MW wind turbine. The development, manufacturing, and certification process depends heavily on being able to validate the full-scale system design and performance under load in both an accredited structural test facility and through accredited field testing. CWP requested that DOE/ NREL upgrade blade test capabilities to perform a scope of work including structural testing of the C-96 blade used on the CWP Liberty turbine. This funds-in CRADA was developed to upgrade NREL blade test capability, while enabling certification testing of the C-96 blade through the facility and equipment upgrades. NREL shared resource funds were used to develop hardware necessary to structurally attach a large wind turbine to the test stand at the NWTC. Participant funds-in monies were used for developing the test program.

  9. Short-pulse generation at 10 μm in an active cw-injected ring laser cavity

    NASA Astrophysics Data System (ADS)

    Bourdet, Gilbert L.

    2003-09-01

    Continuous coherent light conversion in a train of short pulses with good efficiency is possible with a multipass interferometer in which the frequency is shifted at every pass with an acousto-optic frequency shifter. This technique allows one to generate a spectrum made of equidistant components, interferences of which build intense light pulses. Unfortunately, both the width and efficiency of the pulses are limited by the losses undergone by the waves traveling through the interferometer cavity. Improvement of the pulse duration, the peak intensity, and the contrast can be expected in such an experiment when an amplifier is set up inside the cavity. I report on theoretical computations related to this apparatus and apply this theoretical model to a high-pressure CO2 amplifier.

  10. Simulation of the short pulse effects in the start-up from noise in high-gain FELS

    SciTech Connect

    Hahn, S.J.; Kim, K.J.

    1995-12-31

    The spatio-temporal evolution of high-gain free electron lasers from noise is investigated by 1-D simulation calculation. To understand the discrepancy between the experimental result and theoretical prediction of the self-amplified spontaneous emission (SASE), the strong slippage effect in the short pulse electron beam and the coherent bunched beam effect are considered. When the length over which the electron density varies significantly is comparable or smaller than the FEL wavelength, the initial noise level would be increased due to the enhanced coherence between electrons. With a proper computer modeling of the start-up from noise including the energy spread, the overall performance and characteristics of SASE are studied. This work will be helpful to increase the credibility of the simulation calculation to predict the SASE performance in all wave-length regions.

  11. An analysis of short pulse and dual frequency radar techniques for measuring ocean wave spectra from satellites

    NASA Technical Reports Server (NTRS)

    Jackson, F. C.

    1980-01-01

    Scanning beam microwave radars were used to measure ocean wave directional spectra from satellites. In principle, surface wave spectral resolution in wave number can be obtained using either short pulse (SP) or dual frequency (DF) techniques; in either case, directional resolution obtains naturally as a consequence of a Bragg-like wave front matching. A four frequency moment characterization of backscatter from the near vertical using physical optics in the high frequency limit was applied to an analysis of the SP and DF measurement techniques. The intrinsic electromagnetic modulation spectrum was to the first order in wave steepness proportional to the large wave directional slope spectrum. Harmonic distortion was small and was a minimum near 10 deg incidence. NonGaussian wave statistics can have an effect comparable to that in the second order of scattering from a normally distributed sea surface. The SP technique is superior to the DF technique in terms of measurement signal to noise ratio and contrast ratio.

  12. Method for determining the position, angle and other injection parameters of a short pulsed beam in the Brookhaven AGS

    SciTech Connect

    Gardner, C.; Ahrens, L.

    1985-01-01

    As part of the effort to improve the monitoring of the injection process at the Brookhaven Alternating Gradient Synchrotron (AGS), we have developed a beam diagnostics package which processes the signals from the plates of a pick-up electrode (PUE) located near the injection region of the AGS and provides measurements of the position and angle (with respect to the equilibrium orbit) of the injected beam at the stripping foil where the incident H/sup -/ beam is converted into protons. In addition the package provides measurements of the tune and chromaticity of the AGS at injection, and a measurement of the momentum spread of the injected beam. Since these parameters are obtained for a short-pulsed beam at injection we shall refer to the diagnostics package as PIP which stands for Pulsed Injection Parameters.

  13. Remote profiling of lake ice using an S-band short pulse radar aboard an all-terrain vehicle

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    An airborne short-pulse radar system to measure ice thickness was designed. The system supported an effort to develop an all-weather Great Lakes Ice Information System to aid in extending the winter navigation season. Experimental studies into the accuracy and limitations of the system are described. A low power version was operated from an all-terrain vehicle on the Straits of Mackinac during March 1975. The vehicle allowed rapid surveying of large areas and eliminated the ambiguity in location between the radar system and the ground truth ice auger team. It was also possible to the effects of snow cover, surface melt water, pressure ridging, and ice type upon the accuracy of the system. Over 25 sites were explored which had ice thicknesses from 29 to 60 cm. The maximum radar overestimate was 9.8 percent, while the maximum underestimate was 6.6 percent. The average error of the 25 measurements was 0.1 percent.

  14. Isochoric heating of hot dense matter by magnetization of fast electrons produced by ultra-intense short pulse irradiation

    NASA Astrophysics Data System (ADS)

    Sentoku, Y.; Kemp, A.; Bakeman, M.; Presura, R.; Cowan, T. E.

    2006-06-01

    Ultra-intense short-pulse lasers are important tools for creating short-lived high energy plasmas, however to date, it has not been possible, with this method, to create several hundred eV solid density matter because of the rapid transport of the laser-generated hot electrons throughout the target volume. We propose a new way to isochorically heat matter at solid density to extreme temperatures by magnetic confinement of laser-generated hot electrons for several picoseconds by application of a multi-MG external field. In advance of an experiment at the Nevada Terawatt Facility (NTF), using a 100 TW-class laser, which will be synchronized to a 1MA Z-pinch machine, we have performed theoretical studies using a collisional particle-in-cell codes PICLS, which is optimized for a study of isochoric heating of solid density plasmas.

  15. Multi-soliton, multi-breather and higher order rogue wave solutions to the complex short pulse equation

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    In the present paper, we are concerned with the general analytic solutions to the complex short pulse (CSP) equation including soliton, breather and rogue wave solutions. With the aid of a generalized Darboux transformation, we construct the N-bright soliton solution in a compact determinant form, the N-breather solution including the Akhmediev breather and a general higher order rogue wave solution. The first and second order rogue wave solutions are given explicitly and analyzed. The asymptotic analysis is performed rigorously for both the N-soliton and the N-breather solutions. All three forms of the analytical solutions admit either smoothed-, cusped- or looped-type ones for the CSP equation depending on the parameters. It is noted that, due to the reciprocal (hodograph) transformation, the rogue wave solution to the CSP equation can be a smoothed, cusponed or a looped one, which is different from the rogue wave solution found so far.

  16. Self-consistent particle-in-cell modelling of short pulse absorption and transport for high energy density physics experiments

    NASA Astrophysics Data System (ADS)

    Ramsay, M. G.; Arber, T. D.; Sircombe, N. J.

    2016-03-01

    In order for detailed, solid density particle-in-cell (PIC) simulations to run within a reasonable time frame, novel approaches to modelling high density material must be employed. For the purposes of modelling high intensity, short pulse laser-plasma interactions, however, these approaches must be consistent with retaining a full PIC model in the low-density laser interaction region. By replacing the standard Maxwell field solver with an electric field update based on a simplified Ohm's law in regions of high electron density, it is possible to access densities at and above solid without being subject to the standard grid and time step constraints. Such a model has recently been implemented in the PIC code EPOCH. We present the initial results of a detailed two-dimensional simulation performed to compare the adapted version of the code with recent experimental results from the Orion laser facility.

  17. Remote sensing of atmospheric pressure and sea state from satellites using short-pulse multicolor laser altimeters

    NASA Technical Reports Server (NTRS)

    Gardner, C. S.; Tsai, B. M.; Abshire, J. B.

    1983-01-01

    Short pulse multicolor laser ranging systems are currently being developed for satellite ranging applications. These systems use Q-switched pulsed lasers and streak tube cameras to provide timing accuracies approaching a few picoseconds. Satellite laser ranging systems was used to evaluate many important geophysical phenomena such as fault motion, polar motion and solid earth tides, by measuring the orbital perturbations of retroreflector equipped satellites. Some existing operational systems provide range resolution approaching a few millimeters. There is currently considerable interest in adapting these highly accurate systems for use as airborne and satellite based altimeters. Potential applications include the measurement of sea state, ground topography and atmospheric pressure. This paper reviews recent progress in the development of multicolor laser altimeters for use in monitoring sea state and atmospheric pressure.

  18. 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}.

  19. Properties of High-Frequency Sub-Wavelength Ripples on Stainless Steel 304L under Ultra Short Pulse Laser Irradiation

    NASA Astrophysics Data System (ADS)

    Mitko, V. S.; Römer, G. R. B. E.; Veld, A. J. Huis in `t.; Skolski, J. Z. P.; Obona, J. V.; Ocelík, V.; De Hosson, J. T. M.

    The paper concentrates on surface texturing on sub-micro meter scale with ultra short laser pulses that has several applications, e.g. changing the hydrophilic/hydrophobic performance, optical or tribological properties of materials. In general, the formations of wavy structures, or ripples on a surface irradiated by short pulse lasers has been observed experimentally since 1965, and are usually referred to as Laser Induced Periodic Surface Structures (LIPSS). Generally Low Spatial Frequency LIPSS (LSFL) and High Spatial Frequency LIPSS (HSFL) are observed. The existing theoretical models do not describe the origin, nor growth of the ripples satisfactorily. That is why the experimental approach still plays a leading role in the investigation of ripple formation. In this paper we study the development of HSFL and LSFL as a result of picosecond laser pulses on a surface of stainless steel. Influences of number of pulses and pulse overlap on ripples growth were examined.

  20. Investigating short-pulse shock initiation in HMX-based explosives with reactive meso-scale simulations

    NASA Astrophysics Data System (ADS)

    Springer, H. K.; Tarver, C. M.; Reaugh, J. E.; May, C. M.

    2014-05-01

    We performed reactive meso-scale simulations of short-pulse experiments to study the influence of flyer velocity and pore structure on shock initiation of LX-10 (95wt% HMX, 5wt% Viton A). Our calculations show that the reaction evolution fit a power law relationship in time and increases with increasing porosity, decreasing pore size, and increasing flyer velocity. While heterogeneous shock initiation modes, dependent on hot spot mechanisms, are predicted at lower flyer velocities, mixed heterogeneous-homogeneous shock initiation modes, less dependent on hot spots, are predicted at higher velocities. These studies are important because they enable the development of predictive shock initiation models that incorporate complex microstructure and can be used to optimize performance-safety characteristics of explosives.

  1. 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.

  2. The new methods of treatment for age-related macular degeneration using the ultra-short pulsed laser

    NASA Astrophysics Data System (ADS)

    Iwamoto, Yumiko; Awazu, Kunio; Suzuki, Sachiko; Ohshima, Tetsuro; Sawa, Miki; Sakaguchi, Hirokazu; Tano, Yasuo; Ohji, Masahito

    2007-02-01

    The non-invasive methods of treatments have been studying for the improvement of quality of life (QOL) of patients undergoing treatment. A photodynamic therapy (PDT) is one of the non-invasive treatments. PDT is the methods of treatment using combination of a laser and a photosensitizer. PDT has few risks for patients. Furthermore, PDT enables function preservation of a disease part. PDT has been used for early cancer till now, but in late years it is applied for age-related macular degeneration (AMD). AMD is one of the causes of vision loss in older people. However, PDT for AMD does not produce the best improvement in visual acuity. The skin photosensivity by an absorption characteristic of a photosensitizer is avoided. We examined new PDT using combination of an ultra-short pulsed laser and indocyanine green (ICG).

  3. Laser Processing of Carbon Fiber Reinforced Plastics - Release of Carbon Fiber Segments During Short-pulsed Laser Processing of CFRP

    NASA Astrophysics Data System (ADS)

    Walter, Juergen; Brodesser, Alexander; Hustedt, Michael; Bluemel, Sven; Jaeschke, Peter; Kaierle, Stefan

    Cutting and ablation using short-pulsed laser radiation are promising technologies to produce or repair CFRP components with outstanding mechanical properties e.g. for automotive and aircraft industry. Using sophisticated laser processing strategies and avoiding excessive heating of the workpiece, a high processing quality can be achieved. However, the interaction of laser radiation and composite material causes a notable release of hazardous substances from the process zone, amongst others carbon fiber segments or fibrous particles. In this work, amounts and geometries of the released fiber segments are analyzed and discussed in terms of their hazardous potential. Moreover, it is investigated to what extent gaseous organic process emissions are adsorbed at the fiber segments, similar to an adsorption of volatile organic compounds at activated carbon, which is typically used as filter material.

  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. Short-pulse controlled optical switch using external cavity based single mode Fabry-Pérot laser diode.

    PubMed

    Nakarmi, Bikash; Hoai, Tran Quoc; Won, Yong-Hyub; Zhang, Xuping

    2014-06-30

    We propose and demonstrate a novel scheme for short pulse controlled all-optical switch using external cavity based single mode Fabry- Pérot laser diode (SMFP-LD). The proposed scheme consists of control unit and switching unit as two essential blocks. The basic principle of the proposed scheme is the optical bistability property of SMFP-LD for the control unit and the suppression of the dominant beam of SMFP-LD with injection locking for the switching unit. We also present the analysis of hysteresis width and rising/falling time with change in wavelength detuning which helps to find the optimum wavelength detuning value and power of light beams at different stages of the proposed scheme that gives wide input dynamic power range, high ON/OFF contrast ratio, and low rising/falling time. Input data of 10 Gb/s Non Return to Zero (NRZ) signal is switched at output ports depending upon the control signal generated by the control unit, which comprises of optical SR latch. Output waveforms, clear eye diagrams with extinction ratio of about 11 dB, rising/falling time of about 30 ps and 40 ps, and bit error rate (BER) are measured to validate proposed scheme. No noise floor is observed at output ports up to BER of 10-(12) and the maximum power penalty recorded is about 1.7 dB at a BER of 10-(9) which shows good performance of the proposed short pulse controlled optical switch using SMFP-LDs.

  6. 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.

  7. Characterisation of virus transport and attenuation in epikarst using short pulse and prolonged injection multi-tracer testing.

    PubMed

    Flynn, Raymond M; Sinreich, Michael

    2010-02-01

    Attenuation processes controlling virus fate and transport in the vadose zone of karstified systems can strongly influence groundwater quality. This research compares the breakthrough of two bacteriophage tracers (H40/1 and T7), with contrasting properties, at subsurface monitoring points following application onto an overlying composite sequence of thin organic soil and weathered limestone (epikarst). Short pulse multi-tracer test results revealed that T7 (Source concentration, Co=1.8x10(6)pfu/mL) and H40/1 (Co=5.9x10(6)pfu/mL) could reach sampling points 10 m below ground less than 30 min after tracer application. Contrasting deposition rates, determined from simulated tracer responses, reflected the potential of the ground to differentially attenuate viruses. Prolonged application of both T7 (Co=2.3x10(4)pfu/mL) and H40/1 (Co=1.3x10(5)pfu/mL) over a five hour period during a subsequent test, in which ionic strength levels observed at monitoring points rose consistently, corresponded to a rapid rise in T7 levels, followed by a gradual decline before the end of tracer injection; this reflected reaction-limited deposition in the system. T7's response contrasted with that of H40/1, whose concentration remained constant over a three hour period before declining dramatically prior to the end of tracer injection. Subsequent application of lower ionic strength tracer-free flush water generated a rapid rise in H40/1 levels and a more gradual release of T7. Results highlight the benefits of employing prolonged injection multi-tracer tests for identifying processes not apparent from conventional short pulse tests. Study findings demonstrate that despite rapid transport rates, the epikarst is capable of physicochemical filtration of viruses and their remobilization, depending on virus type and hydrochemical conditions. Crown Copyright 2009. Published by Elsevier Ltd. All rights reserved.

  8. Fiber Bragg grating temperature sensors in a 6.5-MW generator exciter bridge and the development and simulation of its thermal model.

    PubMed

    de Morais Sousa, Kleiton; Probst, Werner; Bortolotti, Fernando; Martelli, Cicero; da Silva, Jean Carlos Cardozo

    2014-09-05

    This work reports the thermal modeling and characterization of a thyristor. The thyristor is used in a 6.5-MW generator excitation bridge. Temperature measurements are performed using fiber Bragg grating (FBG) sensors. These sensors have the benefits of being totally passive and immune to electromagnetic interference and also multiplexed in a single fiber. The thyristor thermal model consists of a second order equivalent electric circuit, and its power losses lead to an increase in temperature, while the losses are calculated on the basis of the excitation current in the generator. Six multiplexed FBGs are used to measure temperature and are embedded to avoid the effect of the strain sensitivity. The presented results show a relationship between field current and temperature oscillation and prove that this current can be used to determine the thermal model of a thyristor. The thermal model simulation presents an error of 1.5 °C, while the FBG used allows for the determination of the thermal behavior and the field current dependence. Since the temperature is a function of the field current, the corresponding simulation can be used to estimate the temperature in the thyristors.

  9. Fiber Bragg Grating Temperature Sensors in a 6.5-MW Generator Exciter Bridge and the Development and Simulation of Its Thermal Model

    PubMed Central

    de Morais Sousa, Kleiton; Probst, Werner; Bortolotti, Fernando; Martelli, Cicero; da Silva, Jean Carlos Cardozo

    2014-01-01

    This work reports the thermal modeling and characterization of a thyristor. The thyristor is used in a 6.5-MW generator excitation bridge. Temperature measurements are performed using fiber Bragg grating (FBG) sensors. These sensors have the benefits of being totally passive and immune to electromagnetic interference and also multiplexed in a single fiber. The thyristor thermal model consists of a second order equivalent electric circuit, and its power losses lead to an increase in temperature, while the losses are calculated on the basis of the excitation current in the generator. Six multiplexed FBGs are used to measure temperature and are embedded to avoid the effect of the strain sensitivity. The presented results show a relationship between field current and temperature oscillation and prove that this current can be used to determine the thermal model of a thyristor. The thermal model simulation presents an error of 1.5 °C, while the FBG used allows for the determination of the thermal behavior and the field current dependence. Since the temperature is a function of the field current, the corresponding simulation can be used to estimate the temperature in the thyristors. PMID:25198007

  10. FY05 LDRD Final ReportTime-Resolved Dynamic Studies using Short Pulse X-Ray Radiation

    SciTech Connect

    Nelson, A; Dunn, J; van Buuren, T; Budil, K; Sadigh, B; Gilmer, G; Falcone, R; Lee, R; Ng, A

    2006-02-10

    Established techniques must be extended down to the ps and sub-ps time domain to directly probe product states of materials under extreme conditions. We used short pulse ({le} 1 ps) x-ray radiation to track changes in the physical properties in tandem with measurements of the atomic and electronic structure of materials undergoing fast laser excitation and shock-related phenomena. The sources included those already available at LLNL, including the picosecond X-ray laser as well as the ALS Femtosecond Phenomena beamline and the SSRL based sub-picosecond photon source (SPPS). These allow the temporal resolution to be improved by 2 orders of magnitude over the current state-of-the-art, which is {approx} 100 ps. Thus, we observed the manifestations of dynamical processes with unprecedented time resolution. Time-resolved x-ray photoemission spectroscopy and x-ray scattering were used to study phase changes in materials with sub-picosecond time resolution. These experiments coupled to multiscale modeling allow us to explore the physics of materials in high laser fields and extreme non-equilibrium states of matter. The ability to characterize the physical and electronic structure of materials under extreme conditions together with state-of-the-art models and computational facilities will catapult LLNL's core competencies into the scientific world arena as well as support its missions of national security and stockpile stewardship.

  11. 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

  12. 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.

  13. Numerical simulation of high-power virtual-cathode reflex triode driven by repetitive short pulse electron gun

    SciTech Connect

    Yovchev, I.G.; Spassovsky, I.P.; Nikolov, N.A.; Dimitrov, D.P.; Messina, G.; Raimondi, P.; Barroso, J.J.; Correa, R.A.

    1996-06-01

    A virtual-cathode reflex triode is investigated by numerical simulations. A trapezoidal in shape voltage pulse with an amplitude of 300 kV is applied to the solid cathode of the device to drive the cathode negative. The electron beam-to-microwave power conversion efficiency {epsilon}, calculated for the pulse flat top with a duration {tau}{sub ft} = 1.2 ns is approximately the same (about 1.5--2%) as well as for a long flat top ({tau}{sub ft} = 4 ns). The simulations show a 10--15% increase of {epsilon} at {tau}{sub ft} shortening to 0.6 ns. However, this occurs when the anode mesh transparency is high (80--90%). Considerable enhancement of the efficiency (about four times) for {tau}{sub ft} = 0.6 ns has been calculated if the cathode side surface is brought near to the anode tube (from {approx}0.5% at cathode radius R{sub c} = 1.6 cm to {approx}2% at R{sub c} = 3.8 cm). The obtained results would find an application for the design of virtual-cathode reflex triode devices driven by a short pulse and high repetition rate electron gun.

  14. 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.

  15. Transition from interpulse to afterglow plasmas driven by repetitive short-pulse microwaves in a multicusp magnetic field

    NASA Astrophysics Data System (ADS)

    Pandey, Shail; Sahu, Debaprasad; Bhattacharjee, Sudeep

    2012-08-01

    In the power-off phase, plasmas generated by repetitive short-pulse microwaves in a multicusp magnetic field show a transitive nature from interpulse to afterglow as a function of pulse duration tw = 20-200 μs. The ionized medium can be driven from a highly non equilibrium to an equilibrium state inside the pulses, thereby dictating the behavior of the plasma in the power-off phase. Compared to afterglows, interpulse plasmas observed for tw < 50 μs are characterized by a quasi-steady-state in electron density that persists for ˜ 20-40 μs even after the end of the pulse and has a relatively slower decay rate (˜ 4.3 × 104 s-1) of the electron temperature, as corroborated by optical measurements. The associated electron energy probability function indicates depletion in low energy electrons which appear at higher energies just after the end of the pulse. The transition occurs at tw ˜ 50 μs as confirmed by time evolution of integrated electron numbers densities obtained from the distribution function.

  16. Investigation of stimulated raman scattering using short-pulse diffraction limited laser beam near the instability threshold

    SciTech Connect

    Kline, John L; Montgomery, David S; Flippo, Kirk A; Rose, Harvey A; Yin, L; Albright, B J; Johnson, R P; Shimada, T; Bowers, K; Rousseaux, C; Tassin, V; Baton, S D; Amiranoff, F; Hardin, R A

    2008-01-01

    Short pulse laser plasma interaction experiments using diffraction limited beams provide an excellent platform to investigate the fundamental physics of Stimulated Raman Scattering. Detailed understanding of these laser plasma instabilities impacts the current inertial confinement fusion ignition designs and could potentially impact fast ignition when higher energy lasers are used with longer pulse durations ( > 1 kJ and> 1 ps). Using short laser pulses, experiments can be modeled over the entire interaction time of the laser using particle-in-cell codes to validate our understanding quantitatively. Experiments have been conducted at the Trident laser facility and the LULI (Laboratoire pour l'Utilisation des Lasers Intenses) to investigate stimulated Raman scattering near the threshold of the instability using 527 nm and 1059 nm laser light respectively with 1.5-3.0 ps pulses. In both experiments, the interaction beam was focused into a pre-ionized He gas-jet plasma. Measurements of the reflectivity as a function of intensity and k{lambda}{sub D} were completed at the Trident laser facility. At LULI, a 300 fs Thomson scattering probe is used to directly measure the density fluctuations of the driven electron plasma and ion acoustic waves. Work is currently underway comparing the results of the experiments with simulations using the VPIC [K. J. Bowers, et at., Phys. Plasmas, 15 055703 (2008)] particle-in-cell code. Details of the experimental results are presented in this manuscript.

  17. The Description of Extremely Short Pulses in Non-Resonant Media in Frame of Maxwell-Duffing-Type Models

    NASA Astrophysics Data System (ADS)

    Kazantseva, Elena V.

    The propagation of extremely short pulses of electromagnetic field (electromagnetic spikes) is considered in the framework of a model where the material medium is represented by anharmonic oscillators with cubic nonlinearities (Duffing model) and waves can propagate in both directions. The system of total Maxwell-Duffing equations admits two families of exact analytical solutions in the form of solitary waves. The single-cycle electromagnetic pulse propagation in a medium whose dispersion and nonlinear properties are described by the cubic-quintic Duffing model (oscillator with third- and fifth-order anharmonicity). A system of equations governing the evolution of a unidirectional electromagnetic wave is analyzed without using the approximation of slowly varying envelopes. Three types of solutions of this system describing stationary propagation of a pulse in such a medium are found. When the signs of the anharmonicity constants are different, the amplitude of a steady-state pulse is limited, but its energy may grow on account of an increase in its duration.

  18. Magneto acoustic tomography with short pulsed magnetic field for in-vivo imaging of magnetic iron oxide nanoparticles.

    PubMed

    Mariappan, Leo; Shao, Qi; Jiang, Chunlan; Yu, Kai; Ashkenazi, Shai; Bischof, John C; He, Bin

    2016-04-01

    Nanoparticles are widely used as contrast and therapeutic agents. As such, imaging modalities that can accurately estimate their distribution in-vivo are actively sought. We present here our method Magneto Acoustic Tomography (MAT), which uses magnetomotive force due to a short pulsed magnetic field to induce ultrasound in the magnetic nanoparticle labeled tissue and estimates an image of the distribution of the nanoparticles in-vivo with ultrasound imaging resolution. In this study, we image the distribution of superparamagnetic iron oxide nanoparticles (IONP) using MAT method. In-vivo imaging was performed on live, nude mice with IONP injected into LNCaP tumors grown subcutaneously within the hind limb of the mice. Our experimental results indicate that the MAT method is capable of imaging the distribution of IONPs in-vivo. Therefore, MAT could become an imaging modality for high resolution reconstruction of MNP distribution in the body. Many magnetic nanoparticles (MNPs) have been used as contrast agents in magnetic resonance imaging. In this study, the authors investigated the use of ultrasound to detect the presence of MNPs by magneto acoustic tomography. In-vivo experiments confirmed the imaging quality of this new approach, which hopefully would provide an alternative method for accurate tumor detection. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. NF-κB signalling and cell fate decisions in response to a short pulse of tumour necrosis factor

    PubMed Central

    Lee, Robin E. C.; Qasaimeh, Mohammad A.; Xia, Xianfang; Juncker, David; Gaudet, Suzanne

    2016-01-01

    In tissues and tumours, cell behaviours are regulated by multiple time-varying signals. While in the laboratory cells are often exposed to a stimulus for the duration of the experiment, in vivo exposures may be much shorter. In this study, we monitored NF-κB and caspase signalling in human cancer cells treated with a short pulse of Tumour Necrosis Factor (TNF). TNF is an inflammatory cytokine that can induce both the pro-survival NF-κB-driven gene transcription pathway and the pro-apoptotic caspase pathway. We find that a few seconds of exposure to TNF is sufficient to activate the NF-κB pathway in HeLa cells and induce apoptotic cell death in both HeLa and Kym-1 cells. Strikingly, a 1-min pulse of TNF can be more effective at killing than a 1-hour pulse, indicating that in addition to TNF concentration, duration of exposure also coordinates cell fate decisions. PMID:28004761

  20. 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.

  1. Transition from interpulse to afterglow plasmas driven by repetitive short-pulse microwaves in a multicusp magnetic field

    SciTech Connect

    Pandey, Shail; Sahu, Debaprasad; Bhattacharjee, Sudeep

    2012-08-15

    In the power-off phase, plasmas generated by repetitive short-pulse microwaves in a multicusp magnetic field show a transitive nature from interpulse to afterglow as a function of pulse duration t{sub w} = 20-200 {mu}s. The ionized medium can be driven from a highly non equilibrium to an equilibrium state inside the pulses, thereby dictating the behavior of the plasma in the power-off phase. Compared to afterglows, interpulse plasmas observed for t{sub w} < 50 {mu}s are characterized by a quasi-steady-state in electron density that persists for {approx} 20-40 {mu}s even after the end of the pulse and has a relatively slower decay rate ({approx} 4.3 Multiplication-Sign 10{sup 4} s{sup -1}) of the electron temperature, as corroborated by optical measurements. The associated electron energy probability function indicates depletion in low energy electrons which appear at higher energies just after the end of the pulse. The transition occurs at t{sub w} {approx} 50 {mu}s as confirmed by time evolution of integrated electron numbers densities obtained from the distribution function.

  2. Coaxial short pulsed laser

    DOEpatents

    Nelson, M.A.; Davies, T.J.

    1975-08-01

    This invention relates to a laser system of rugged design suitable for use in a field environment. The laser itself is of coaxial design with a solid potting material filling the space between components. A reservoir is employed to provide a gas lasing medium between an electrode pair, each of which is connected to one of the coaxial conductors. (auth)

  3. Experimental Characterization of a Grid-Loss Event on a 2.5-MW Dynamometer Using Advanced Operational Modal Analysis: Preprint

    SciTech Connect

    Helsen, J.; Weijtjens, W.; Guo, Y.; Keller, J.; McNiff, B.; Devriendt, C.; Guillaume, P.

    2015-02-01

    This paper experimentally investigates a worst case grid loss event conducted on the National Renewable Energy Laboratory (NREL) Gearbox Reliability Collaborative (GRC) drivetrain mounted on the 2.5MW NREL dynamic nacelle test-rig. The GRC drivetrain has a directly grid-coupled, fixed speed asynchronous generator. The main goal is the assessment of the dynamic content driving this particular assess the dynamic content of the high-speed stage of the GRC gearbox. In addition to external accelerometers, high frequency sampled measurements of strain gauges were used to assess torque fluctuations and bending moments both at the nacelle main shaft and gearbox high-speed shaft (HSS) through the entire duration of the event. Modal analysis was conducted using a polyreference Least Squares Complex Frequency-domain (pLSCF) modal identification estimator. The event driving the torsional resonance was identified. Moreover, the pLSCF estimator identified main drivetrain resonances based on a combination of acceleration and strain measurements. Without external action during the grid-loss event, a mode shape characterized by counter phase rotation of the rotor and generator rotor determined by the drivetrain flexibility and rotor inertias was the main driver of the event. This behavior resulted in significant torque oscillations with large amplitude negative torque periods. Based on tooth strain measurements of the HSS pinion, this work showed that at each zero-crossing, the teeth lost contact and came into contact with the backside flank. In addition, dynamic nontorque loads between the gearbox and generator at the HSS played an important role, as indicated by strain gauge-measurements.

  4. Model development and experimental validation for analyzing initial transients of irradiation of tissues during thermal therapy using short pulse lasers.

    PubMed

    Ganguly, Mohit; Miller, Stephanie; Mitra, Kunal

    2015-11-01

    Short pulse lasers with pulse durations in the range of nanoseconds and shorter are effective in the targeted delivery of heat energy for precise tissue heating and ablation. This photothermal therapy is useful where the removal of cancerous tissue sections is required. The objective of this paper is to use finite element modeling to demonstrate the differences in the thermal response of skin tissue to short-pulse and continuous wave laser irradiation in the initial stages of the irradiation. Models have been developed to validate the temperature distribution and heat affected zone during laser irradiation of excised rat skin samples and live anesthetized mouse tissue. Excised rat skin samples and live anesthetized mice were subjected to Nd:YAG pulsed laser (1,064 nm, 500 ns) irradiation of varying powers. A thermal camera was used to measure the rise in surface temperature as a result of the laser irradiation. Histological analyses of the heat affected zone created in the tissue samples due to the temperature rise were performed. The thermal interaction of the laser with the tissue was quantified by measuring the thermal dose delivered by the laser. Finite element geometries of three-dimensional tissue sections for continuum and vascular models were developed using COMSOL Multiphysics. Blood flow was incorporated into the vascular model to mimic the presence of discrete blood vessels and contrasted with the continuum model without blood perfusion. The temperature rises predicted by the continuum and the vascular models agreed with the temperature rises observed at the surface of the excised rat tissue samples and live anesthetized mice due to laser irradiation respectively. The vascular model developed was able to predict the cooling produced by the blood vessels in the region where the vessels were present. The temperature rise in the continuum model due to pulsed laser irradiation was higher than that due to continuous wave (CW) laser irradiation in the

  5. Study of energy partitioning in mass limited targets using the 50 TW Leopard short-pulse laser

    NASA Astrophysics Data System (ADS)

    Griffin, Brandon; Sawada, Hiroshi; Sentoku, Yasuhiko; Yabuuchi, Toshinori; Chen, Hui; Park, J.-B.; McClean, Harry; Patel, Prav; Beg, Farhat

    2014-10-01

    Mass limited Cu targets were used to study the energy distribution in the interaction of an ultra-intense, short-pulse laser by measuring characteristic x-rays and energetic particles. At the Nevada Terawatt Facility, Leopard delivered 15 J to an 8 μm spot size in a 350 fs pulse, achieving a peak intensity of 1019 W/cm2 at 20° incidence. The 2 μm thick Cu foil targets varied in size from 1 mm2 to 75 μm by 60 μm. A spherical crystal imager and a Bragg crystal x-ray spectrometer were used to measure 8.05 keV monochromatic x-ray images and 7.5-9.5 keV x-rays respectively. A magnet-based electron spectrometer in the rear monitored escaping electrons. Results show a decrease in the absolute yield of both escaped electrons and Cu K-shell x-rays as targets sizes are reduced, while He α emission remains nearly constant. In the smallest target, a bulk temperature of about 150 eV was inferred from the ratio of K β to K α. The interaction of the Leopard laser with the targets was simulated with 2-D implicit Particle-in-cell code PICLS. Comparisons of the simulation and experiment will be presented. This work was supported by the DOE Office of Fusion Energy Science under Fusion Science Center, and the National Nuclear Security Administration under cooperative agreements DE-FC52-06NA27616 and DE-NA0002075. T.Y. was supported by Japan/U.S. Cooperation.

  6. Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters.

    PubMed

    Bello-Silva, Marina Stella; Wehner, Martin; Eduardo, Carlos de Paula; Lampert, Friedrich; Poprawe, Reinhart; Hermans, Martin; Esteves-Oliveira, Marcella

    2013-01-01

    This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach.

  7. Enhancing caries resistance with a short-pulsed CO2 9.3-μm laser: a laboratory study (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Rechmann, Peter; Rechmann, Beate M.; Groves, William H.; Le, Charles; Rapozo-Hilo, Marcia L.; Featherstone, John D. B.

    2016-02-01

    The objective of this laboratory study was to test whether irradiation with a new 9.3µm microsecond short-pulsed CO2-laser enhances enamel caries resistance with and without additional fluoride applications. 101 human enamel samples were divided into 7 groups. Each group was treated with different laser parameters (Carbon-dioxide laser, wavelength 9.3µm, 43Hz pulse-repetition rate, pulse duration between 3μs to 7μs (1.5mJ/pulse to 2.9mJ/pulse). Using a pH-cycling model and cross-sectional microhardness testing determined the mean relative mineral loss delta Z (∆Z) for each group. The pH-cycling was performed with or without additional fluoride. The CO2 9.3μm short-pulsed laser energy rendered enamel caries resistant with and without additional fluoride use.

  8. 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.

  9. Small Gas Bubble Experiment for Mitigation of Cavitation Damage and Pressure Waves in Short-pulse Mercury Spallation Targets

    SciTech Connect

    Wendel, Mark W; Felde, David K; Sangrey, Robert L; Abdou, Ashraf A; West, David L; Shea, Thomas J; Hasegawa, Shoichi; Kogawa, Hiroyuki; Naoe, Dr. Takashi; Farny, Dr. Caleb H.; Kaminsky, Andrew L

    2014-01-01

    Populations of small helium gas bubbles were introduced into a flowing mercury experiment test loop to evaluate mitigation of beam-pulse induced cavitation damage and pressure waves. The test loop was developed and thoroughly tested at the Spallation Neutron Source (SNS) prior to irradiations at the Los Alamos Neutron Science Center - Weapons Neutron Research Center (LANSCE-WNR) facility. Twelve candidate bubblers were evaluated over a range of mercury flow and gas injection rates by use of a novel optical measurement technique that accurately assessed the generated bubble size distributions. Final selection for irradiation testing included two variations of a swirl bubbler provided by Japan Proton Accelerator Research Complex (J-PARC) collaborators and one orifice bubbler developed at SNS. Bubble populations of interest consisted of sizes up to 150 m in radius with achieved gas void fractions in the 10^-5 to 10^-4 range. The nominal WNR beam pulse used for the experiment created energy deposition in the mercury comparable to SNS pulses operating at 2.5 MW. Nineteen test conditions were completed each with 100 pulses, including variations on mercury flow, gas injection and protons per pulse. The principal measure of cavitation damage mitigation was surface damage assessment on test specimens that were manually replaced for each test condition. Damage assessment was done after radiation decay and decontamination by optical and laser profiling microscopy with damaged area fraction and maximum pit depth being the more valued results. Damage was reduced by flow alone; the best mitigation from bubble injection was between half and a quarter that of flow alone. Other data collected included surface motion tracking by three laser Doppler vibrometers (LDV), loop wall dynamic strain, beam diagnostics for charge and beam profile assessment, embedded hydrophones and pressure sensors, and sound measurement by a suite of conventional and contact microphones.

  10. Mechanisms and kinetics of short pulse laser-induced destruction of silver-containing nanoparticles in multicomponent silicate photo-thermo-refractive glass.

    PubMed

    Lumeau, Julien; Glebov, Leonid B

    2014-11-01

    Photo-thermo-refractive (PTR) glass is a photosensitive multi-component silicate glass that is commercially used for the recording of volume holographic elements and finds many applications in advanced laser systems. Refractive index decrement in this glass is observed after UV exposure followed by thermal development. This procedure also causes the appearance of Ag-containing particles that can then be optically bleached by using the second harmonic of a Nd:YAG laser. Despite the broad usage of this method, its mechanisms are still unclear. In this paper, a systematic study of the short pulse laser-induced destruction of Ag-containing particles' kinetics versus incident energy per pulse and dosage is presented. We show that no bleaching of Ag-containing particles occurs for an energy density in laser pulses below 0.1  J/cm2 while above 1  J/cm2, the efficiency of bleaching saturates. Efficiency of bleaching depends on the type of particles to be bleached (Ag, AgBr…). Using a simple model of short pulse laser interaction with nanoparticles embedded in glass, the temperature of the Ag-containing particles reached during the laser interaction is shown to be large enough to produce complete dissipation of these particles which is expected to be the main mechanism of short pulse laser-induced destruction of Ag-containing particles.

  11. Directional spectra of ocean waves from microwave backscatter: A physical optics solution with application to the short-pulse and two-frequency measurement techniques

    NASA Technical Reports Server (NTRS)

    Jackson, F. C.

    1979-01-01

    Two simple microwave radar techniques that are potentially capable of providing routine satellite measurements of the directional spectrum of ocean waves were developed. One technique, the short pulse technique, makes use of very short pulses to resolve ocean surface wave contrast features in the range direction; the other technique, the two frequency correlation technique makes use of coherency in the transmitted waveform to detect the large ocean wave contrast modulation as a beat or mixing frequency in the power backscattered at two closely separated microwave frequencies. A frequency domain analysis of the short pulse and two frequency systems shows that the two measurement systems are essentially duals; they each operate on the generalized (three frequency) fourth-order statistical moment of the surface transfer function in different, but symmetrical ways, and they both measure the same directional contrast modulation spectrum. A three dimensional physical optics solution for the fourth-order moment was obtained for backscatter in the near vertical, specular regime, assuming Gaussian surface statistics.

  12. A treatise on the interaction of molecular systems with short-pulsed highly-intense external fields

    NASA Astrophysics Data System (ADS)

    Paul, Amit K.; Adhikari, Satrajit; Baer, Michael

    2010-11-01

    In this review, we consider two gauges: one, the field-free gauge, is formed by the field-free electronic eigenstates and the other, the field-dressed gauge, is formed by the field-dressed electronic basis set. The field-free gauge is used, of course, in the case of time-independent systems but then it is also the more common one to be used in the case of molecular systems exposed to external fields. This gauge is conceptually simple and therefore numerically friendly - two features which make it versatile for numerical application. The field-dressed gauge is, eventually, more involved but yields deeper insight which might lead to a better understanding of the complicated interaction between a molecular system and external fields. In addition, these features can be exploited to develop efficient and reliable approximations that may save CPU (computer processing unit) time in numerical applications. These two gauges are the main topics of the present review. Once the general derivation of the two gauges is completed, two additional issues are discussed: (i) we extend these gauges to include external fields formed by non-classical photon-state distributions (also known as non-coherent Fock-state distributions). These photon state distributions, recently considered for the first time for molecular systems [A.K. Paul, S. Adhikari, M. Baer, R. Baer, Phys. Rev. A 81 (2010) 013412], are interesting on their own footing. Although here they mainly serve as a vehicle to test the above-mentioned novel approximations, we also devote part of the review to studying the importance of non-coherent Fock states for obtaining an unbiased correct understanding of the interaction of molecular systems with strong, short-pulsed laser fields. For this purpose, we study the photo-dissociation process of H2+ and show (a) that the approximations, recently introduced, diminish the CPU time by about one order of magnitude with minimal loss of accuracy and (b) indeed non-coherent Fock states

  13. Design of the 1.5 MW, 30-96 MHz ultra-wideband 3 dB high power hybrid coupler for Ion Cyclotron Resonance Frequency (ICRF) heating in fusion grade reactor

    NASA Astrophysics Data System (ADS)

    Yadav, Rana Pratap; Kumar, Sunil; Kulkarni, S. V.

    2016-01-01

    Design and developmental procedure of strip-line based 1.5 MW, 30-96 MHz, ultra-wideband high power 3 dB hybrid coupler has been presented and its applicability in ion cyclotron resonance heating (ICRH) in tokamak is discussed. For the high power handling capability, spacing between conductors and ground need to very high. Hence other structural parameters like strip-width, strip thickness coupling gap, and junction also become large which can be gone upto optimum limit where various constrains like fabrication tolerance, discontinuities, and excitation of higher TE and TM modes become prominent and significantly deteriorates the desired parameters of the coupled lines system. In designed hybrid coupler, two 8.34 dB coupled lines are connected in tandem to get desired coupling of 3 dB and air is used as dielectric. The spacing between ground and conductors are taken as 0.164 m for 1.5 MW power handling capability. To have the desired spacing, each of 8.34 dB segments are designed with inner dimension of 3.6 × 1.0 × 40 cm where constraints have been significantly realized, compensated, and applied in designing of 1.5 MW hybrid coupler and presented in paper.

  14. Design of the 1.5 MW, 30-96 MHz ultra-wideband 3 dB high power hybrid coupler for Ion Cyclotron Resonance Frequency (ICRF) heating in fusion grade reactor.

    PubMed

    Yadav, Rana Pratap; Kumar, Sunil; Kulkarni, S V

    2016-01-01

    Design and developmental procedure of strip-line based 1.5 MW, 30-96 MHz, ultra-wideband high power 3 dB hybrid coupler has been presented and its applicability in ion cyclotron resonance heating (ICRH) in tokamak is discussed. For the high power handling capability, spacing between conductors and ground need to very high. Hence other structural parameters like strip-width, strip thickness coupling gap, and junction also become large which can be gone upto optimum limit where various constrains like fabrication tolerance, discontinuities, and excitation of higher TE and TM modes become prominent and significantly deteriorates the desired parameters of the coupled lines system. In designed hybrid coupler, two 8.34 dB coupled lines are connected in tandem to get desired coupling of 3 dB and air is used as dielectric. The spacing between ground and conductors are taken as 0.164 m for 1.5 MW power handling capability. To have the desired spacing, each of 8.34 dB segments are designed with inner dimension of 3.6 × 1.0 × 40 cm where constraints have been significantly realized, compensated, and applied in designing of 1.5 MW hybrid coupler and presented in paper.

  15. Design of the 1.5 MW, 30-96 MHz ultra-wideband 3 dB high power hybrid coupler for Ion Cyclotron Resonance Frequency (ICRF) heating in fusion grade reactor

    SciTech Connect

    Yadav, Rana Pratap Kumar, Sunil; Kulkarni, S. V.

    2016-01-15

    Design and developmental procedure of strip-line based 1.5 MW, 30-96 MHz, ultra-wideband high power 3 dB hybrid coupler has been presented and its applicability in ion cyclotron resonance heating (ICRH) in tokamak is discussed. For the high power handling capability, spacing between conductors and ground need to very high. Hence other structural parameters like strip-width, strip thickness coupling gap, and junction also become large which can be gone upto optimum limit where various constrains like fabrication tolerance, discontinuities, and excitation of higher TE and TM modes become prominent and significantly deteriorates the desired parameters of the coupled lines system. In designed hybrid coupler, two 8.34 dB coupled lines are connected in tandem to get desired coupling of 3 dB and air is used as dielectric. The spacing between ground and conductors are taken as 0.164 m for 1.5 MW power handling capability. To have the desired spacing, each of 8.34 dB segments are designed with inner dimension of 3.6 × 1.0 × 40 cm where constraints have been significantly realized, compensated, and applied in designing of 1.5 MW hybrid coupler and presented in paper.

  16. 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.

  17. Nonablative acne scar reduction after a series of treatments with a short-pulsed 1,064-nm neodymium:YAG laser.

    PubMed

    Lipper, Graeme M; Perez, Maritza

    2006-08-01

    Effective treatment of facial acne scarring presents a major challenge. Nonablative lasers and radiofrequency devices work by thermally stimulating dermal collagen remodeling, thereby softening acne scars in a minimally invasive fashion. One such laser, a 1,064-nm short-pulsed Nd:YAG, uses rapidly scanned low-energy infrared pulses to heat the dermis selectively through the normal dermal microvasculature. In this pilot study, the safety and efficacy of a novel short-pulsed Nd:YAG laser were investigated for the treatment of moderate to severe facial acne scarring. Nine of 10 enrolled patients with moderate to severe facial acne scarring received eight sequential 1,064-nm Nd:YAG treatments (laser parameters 14 J/cm2, 0.3 milliseconds, 5-mm spot size, 7-Hz pulse rate, 2,000 pulses per side of face). Patients were graded for the presence and severity of three scar morphologies: superficial (rolling), medium-depth (boxcar), and deep (ice pick). Outcome measures included blinded evaluation of before and after photographs by three physician observers (scar severity score) and patient self-assessment. Acne scarring improved in 100% of the nine patients completing the study. Scar severity scores improved by a mean of 29.36% (95% confidence interval, 16.93%-41.79%; p = .006); 89% of patients noted greater than 10% scar improvement. No treatment-related adverse events were seen. Our findings support the use of a short-pulsed, low-fluence 1,064-nm Nd:YAG laser as a safe, effective treatment for facial acne scarring. Scar improvement was noted in all treated subjects with minimal discomfort and no downtime. This protocol appears to be most effective at reducing scar depth and softening scar contours. A laser upgrade needed for the study was provided to the authors at a reduced price.

  18. Ion explosion and multi-mega-electron-volt ion generation from an underdense plasma layer irradiated by a relativistically intense short-pulse laser.

    PubMed

    Yamagiwa, M; Koga, J; Tsintsadze, L N; Ueshima, Y; Kishimoto, Y

    1999-11-01

    Ion acceleration and expansion in the interaction of a relativistically intense short-pulse laser with an underdense plasma layer are investigated. Ion and electron dynamics are studied by a two-dimensional particle-in-cell simulation with the real mass ratio. It is shown that the longitudinal electric field induced by electron evacuation due to a large ponderomotive force or light pressure can accelerate ions to several MeV in the direction of the laser propagation. It is after the laser completely passes through the plasma layer that the ion explosion starts to be significant.

  19. High-peak-power, short-pulse-width, LD end-pumped, passively Q-switched Nd:YAG 946 nm laser

    NASA Astrophysics Data System (ADS)

    Yan, Renpeng; Yu, Xin; Ma, Yufei; Li, Xudong; Chen, Deying; Yu, Junhua

    2012-10-01

    High-peak-power, short-pulse-width diode pumped 946 nm Nd:YAG laser in passively Q-switching operation with Cr4+:YAG is reported. The highest average output power reaches 3.4 W using the Cr4+:YAG with initial transmissivity T0=95%. When the T0=90% Cr4+:YAG is employed, the maximum peak power of 31.4 kW with a pulse width of 8.3 ns at 946 nm is generated.

  20. 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.

  1. Dynamics of shock waves and cavitation bubbles in bilinear elastic-plastic media, and the implications to short-pulsed laser surgery

    NASA Astrophysics Data System (ADS)

    Brujan, E.-A.

    2005-01-01

    The dynamics of shock waves and cavitation bubbles generated by short laser pulses in water and elastic-plastic media were investigated theoretically in order to get a better understanding of their role in short-pulsed laser surgery. Numerical simulations were performed using a spherical model of bubble dynamics which include the elastic-plastic behaviour of the medium surrounding the bubble, compressibility, viscosity, density and surface tension. Breakdown in water produces a monopolar acoustic signal characterized by a compressive wave. Breakdown in an elastic-plastic medium produces a bipolar acoustic signal, with a leading positive compression wave and a trailing negative tensile wave. The calculations revealed that consideration of the tissue elasticity is essential to describe the bipolar shape of the shock wave emitted during optical breakdown. The elastic-plastic response of the medium surrounding the bubble leads to a significant decrease of the maximum size of the cavitation bubble and pressure amplitude of the shock wave emitted during bubble collapse, and shortening of the oscillation period of the bubble. The results are discussed with respect to collateral damage in short-pulsed laser surgery.

  2. A short pulse (7 {mu}s FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams

    SciTech Connect

    Irimia, Daniel; Dobrikov, Dimitar; Kortekaas, Rob; Voet, Han; Janssen, Maurice H. M.; Ende, Daan A. van den; Groen, Wilhelm A.

    2009-11-15

    In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 {mu}s have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 {mu}m nozzle releases about 10{sup 16} particles/pulse and the beam brightness was estimated to be 4x10{sup 22} particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5x10{sup -6} Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow ({Delta}v/v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas

  3. A short pulse (7 μs FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams

    NASA Astrophysics Data System (ADS)

    Irimia, Daniel; Dobrikov, Dimitar; Kortekaas, Rob; Voet, Han; van den Ende, Daan A.; Groen, Wilhelm A.; Janssen, Maurice H. M.

    2009-11-01

    In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 μs have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 μm nozzle releases about 1016 particles/pulse and the beam brightness was estimated to be 4×1022 particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5×10-6 Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Δv /v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the cantilever

  4. A short pulse (7 micros FWHM) and high repetition rate (dc-5 kHz) cantilever piezovalve for pulsed atomic and molecular beams.

    PubMed

    Irimia, Daniel; Dobrikov, Dimitar; Kortekaas, Rob; Voet, Han; van den Ende, Daan A; Groen, Wilhelm A; Janssen, Maurice H M

    2009-11-01

    In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 micros have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 microm nozzle releases about 10(16) particles/pulse and the beam brightness was estimated to be 4x10(22) particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5x10(-6) Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Delta v/v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the

  5. Two-dimensional time-resolved ultra-high speed imaging of K-alpha emission from short-pulse-laser interactions to observe electron recirculation

    DOE PAGES

    Nagel, S. R.; Chen, H.; Park, J.; ...

    2017-04-04

    Time resolved x-ray images with 7 ps resolution are recorded on relativistic short-pulse laser-plasma experiments using the dilation x-ray imager, a high-speed x-ray framing camera, sensitive to x-rays in the range of ≈1-17 keV. Furthermore, this capability enables a series of 2D x-ray images to be recorded at picosecond scales, which allows for the investigation of fast electron transport within the target with unprecedented temporal resolution. With an increase in the Kα-emission spot size over time we found that targets were thinner than the recirculation limit and is absent for thicker targets. Together with the observed polarization dependence of themore » spot size increase, this indicates that electron recirculation is relevant for the x-ray production in thin targets.« less

  6. 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.

  7. Study of silver K{alpha} and bremsstrahlung radiation from short-pulse laser-matter interactions with applications for x-ray radiography

    SciTech Connect

    Westover, B.; Beg, F. N.; MacPhee, A.; Chen, C.; Hey, D.; Maddox, B.; Park, H.-S.; Remington, B.; Ma, T.

    2010-08-15

    Measurements of K{alpha} radiation yield and x-ray bremsstrahlung emission from thin-foil silver targets are presented. The targets were irradiated by a short pulse laser with intensities from 5x10{sup 16} to 10{sup 18} W/cm{sup 2} at 40 ps. Single hit charge-coupled device detectors, differential filter-stack detectors, and a crystal spectrometer were used to investigate the angular distribution of the K{alpha} and bremsstrahlung x-rays. This study is the first to use a broadband detector to estimate the absolute numbers of K{alpha} photons and to determine K{alpha} to bremsstrahlung ratios. The relevance of this work in the context of x-ray diffraction and x-ray radiography is discussed.

  8. 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.

  9. Kinetic study on non-thermal volumetric plasma decay in the early afterglow of air discharge generated by a short pulse microwave or laser

    SciTech Connect

    Yang, Wei Zhou, Qianhong; Dong, Zhiwei

    2016-08-28

    This paper reports a kinetic study on non-thermal plasma decay in the early afterglow of air discharge generated by short pulse microwave or laser. A global self-consistent model is based on the particle balance of complex plasma chemistry, electron energy equation, and gas thermal balance equation. Electron-ion Coulomb collision is included in the steady state Boltzmann equation solver to accurately describe the electron mobility and other transport coefficients. The model is used to simulate the afterglow of microsecond to nanosecond pulse microwave discharge in N{sub 2}, O{sub 2}, and air, as well as femtosecond laser filament discharge in dry and humid air. The simulated results for electron density decay are in quantitative agreement with the available measured ones. The evolution of plasma decay under an external electric field is also investigated, and the effect of gas heating is considered. The underlying mechanism of plasma density decay is unveiled through the above kinetic modeling.

  10. Influence of irradiation by a novel CO2 9.3-μm short-pulsed laser on sealant bond strength.

    PubMed

    Rechmann, P; Sherathiya, K; Kinsel, R; Vaderhobli, R; Rechmann, B M T

    2017-04-01

    The objective of this in vitro study was to evaluate whether irradiation of enamel with a novel CO2 9.3-μm short-pulsed laser using energies that enhance caries resistance influences the shear bond strength of composite resin sealants to the irradiated enamel. Seventy bovine and 240 human enamel samples were irradiated with a 9.3-μm carbon dioxide laser (Solea, Convergent Dental, Inc., Natick, MA) with four different laser energies known to enhance caries resistance or ablate enamel (pulse duration from 3 μs at 1.6 mJ/pulse to 43 μs at 14.9 mJ/pulse with fluences between 3.3 and 30.4 J/cm(2), pulse repetition rate between 4.1 and 41.3 Hz, beam diameter of 0.25 mm and 1-mm spiral pattern, and focus distance of 4-15 mm). Irradiation was performed "freehand" or using a computerized, motor-driven stage. Enamel etching was achieved with 37% phosphoric acid (Scotchbond Universal etchant, 3M ESPE, St. Paul, MN). As bonding agent, Adper Single Bond Plus was used followed by placing Z250 Filtek Supreme flowable composite resin (both 3M ESPE). After 24 h water storage, a single-plane shear bond test was performed (UltraTester, Ultradent Products, Inc., South Jordan, UT). All laser-irradiated samples showed equal or higher bond strength than non-laser-treated controls. The highest shear bond strength values were observed with the 3-μs pulse duration/0.25-mm laser pattern (mean ± SD = 31.90 ± 2.50 MPa), representing a significant 27.4% bond strength increase over the controls (25.04 ± 2.80 MPa, P ≤ 0.0001). Two other caries-preventive irradiation (3 μs/1 mm and 7 μs/0.25 mm) and one ablative pattern (23 μs/0.25 mm) achieved significantly increased bond strength compared to the controls. Bovine enamel also showed in all test groups increased shear bond strength over the controls. Computerized motor-driven stage irradiation did not show superior bond strength values over the clinically more relevant freehand irradiation. Enamel

  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. 5MW Raft River Facility Experience

    SciTech Connect

    Whitbeck, J.F.

    1980-12-01

    Located in Northern California In Lake and Sonoma Counties about 90 miles north of San Francisco, Pacific Gas and Electric Company's (PG and E's) The Geysers Power Plant, which has at present fourteen units in service with a net generating capacity of 798MW, is the largest geothermal development in the world. Eight additional PG and E units now in construction, design, and planning will add 720MW of additional capacity by 1986. Figure 1 shows the location of this project and the locations of the existing and future units. This paper discusses evolution of Geysers Unit 18 through resource and project planning, licensing, design, and what is expected during construction, and startup. While many of the experiences are unique to The Geysers units, some could be applicable to other geothermal developments. This unit is one of a series of 110MW units of standardized design which are being developed to reduce the cost and improve schedules. Construction has just commenced, and it is expected to be in commercial operation in October 1982.

  13. Comparative study of low-pressure rare-gas fluoride/chloride lasers excited by a short-pulse electron beam

    SciTech Connect

    Suda, A.; Kumagai, H.; Izawa, S.; Obara, M.

    1988-08-15

    Output characteristics of the short-pulse electron-beam excited ArF (193 nm), KrF (248 nm), XeF (351 nm), KrCl (222 nm), and XeCl (308 nm) lasers were experimentally investigated at the same time on the same device for various mixtures all pumped at a high excitation rate of 2.3 MW/cm/sup 3/. The optimum pressure of rare gas forming its rare-gas halide excimer increased for the sequence of ArF, KrCl, KrF, XeCl, and XeF, indicating that rare-gas halides were more quenched by the heavier rare gases, such as Xe, even at near-atmospheric pressures. At nearly atmospheric pressures the Ar-buffered mixtures gave higher laser energy than Ne-buffered mixtures except for the XeF laser. Through a series of measurements, the ArF laser showed the best result on the output energy of 96 J (5 J/l-script ) with an intrinsic efficiency of 3.4%.

  14. High-resolution measurements of the spatial and temporal evolution of megagauss magnetic fields created in intense short-pulse laser-plasma interactions

    SciTech Connect

    Chatterjee, Gourab Singh, Prashant Kumar; Adak, Amitava; Lad, Amit D.; Kumar, G. Ravindra

    2014-01-15

    A pump-probe polarimetric technique is demonstrated, which provides a complete, temporally and spatially resolved mapping of the megagauss magnetic fields generated in intense short-pulse laser-plasma interactions. A normally incident time-delayed probe pulse reflected from its critical surface undergoes a change in its ellipticity according to the magneto-optic Cotton-Mouton effect due to the azimuthal nature of the ambient self-generated megagauss magnetic fields. The temporal resolution of the magnetic field mapping is typically of the order of the pulsewidth, limited by the laser intensity contrast, whereas a spatial resolution of a few μm is achieved by this optical technique. High-harmonics of the probe can be employed to penetrate deeper into the plasma to even near-solid densities. The spatial and temporal evolution of the megagauss magnetic fields at the target front as well as at the target rear are presented. The μm-scale resolution of the magnetic field mapping provides valuable information on the filamentary instabilities at the target front, whereas probing the target rear mirrors the highly complex fast electron transport in intense laser-plasma interactions.

  15. The Influence of High-Power Ion Beams and High-Intensity Short-Pulse Implantation of Ions on the Properties of Ceramic Silicon Carbide

    NASA Astrophysics Data System (ADS)

    Kabyshev, A. V.; Konusov, F. V.; Pavlov, S. K.; Remnev, G. E.

    2016-02-01

    The paper is focused on the study of the structural, electrical and optical characteristics of the ceramic silicon carbide before and after irradiation in the regimes of the high-power ion beams (HPIB) and high-intensity short-pulse implantation (HISPI) of carbon ions. The dominant mechanism of transport of charge carriers, their type and the energy spectrum of localized states (LS) of defects determining the properties of SiC were established. Electrical and optical characteristics of ceramic before and after irradiation are determined by the biographical and radiation defects whose band gap (BG) energy levels have a continuous energetic distribution. A dominant p-type activation component of conduction with participation of shallow acceptor levels 0.05-0.16 eV is complemented by hopping mechanism of conduction involving the defects LS with a density of 1.2T017-2.4T018 eV-Am-3 distributed near the Fermi level.The effect of radiation defects with deep levels in the BG on properties change dominates after HISPI. A new material with the changed electronic structure and properties is formed in the near surface layer of SiC after the impact of the HPIB.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Thermoacoustic Imaging and Therapy Guidance based on Ultra-short Pulsed Microwave Pumped Thermoelastic Effect Induced with Superparamagnetic Iron Oxide Nanoparticles.

    PubMed

    Wen, Liewei; Yang, Sihua; Zhong, Junping; Zhou, Quan; Xing, Da

    2017-01-01

    Multifunctional nanoparticle-mediated imaging and therapeutic techniques are promising modalities for accurate localization and targeted treatment of cancer in clinical settings. Thermoacoustic (TA) imaging is highly sensitive to detect the distribution of water, ions or specific nanoprobes and provides excellent resolution, good contrast and superior tissue penetrability. TA therapy is a potential non-invasive approach for the treatment of deep-seated tumors. In this study, human serum albumin (HSA)-functionalized superparamagnetic iron oxide nanoparticle (HSA-SPIO) is used as a multifunctional nanoprobe with clinical application potential for MRI, TA imaging and treatment of tumor. In addition to be a MRI contrast agent for tumor localization, HSA-SPIO can absorb pulsed microwave energy and transform it into shockwave via the thermoelastic effect. Thereby, the reconstructed TA image by detecting TA signal is expected to be a sensitive and accurate representation of the HSA-SPIO accumulation in tumor. More importantly, owing to the selective retention of HSA-SPIO in tumor tissues and strong TA shockwave at the cellular level, HSA-SPIO induced TA effect under microwave-pulse radiation can be used to highly-efficiently kill cancer cells and inhibit tumor growth. Furthermore, ultra-short pulsed microwave with high excitation efficiency and deep penetrability in biological tissues makes TA therapy a highly-efficient anti-tumor modality on the versatile platform. Overall, HSA-SPIO mediated MRI and TA imaging would offer more comprehensive diagnostic information and enable dynamic visualization of nanoagents in the tumorous tissue thereby tumor-targeted therapy.

  2. Thermoacoustic Imaging and Therapy Guidance based on Ultra-short Pulsed Microwave Pumped Thermoelastic Effect Induced with Superparamagnetic Iron Oxide Nanoparticles

    PubMed Central

    Wen, Liewei; Yang, Sihua; Zhong, Junping; Zhou, Quan; Xing, Da

    2017-01-01

    Multifunctional nanoparticle-mediated imaging and therapeutic techniques are promising modalities for accurate localization and targeted treatment of cancer in clinical settings. Thermoacoustic (TA) imaging is highly sensitive to detect the distribution of water, ions or specific nanoprobes and provides excellent resolution, good contrast and superior tissue penetrability. TA therapy is a potential non-invasive approach for the treatment of deep-seated tumors. In this study, human serum albumin (HSA)-functionalized superparamagnetic iron oxide nanoparticle (HSA-SPIO) is used as a multifunctional nanoprobe with clinical application potential for MRI, TA imaging and treatment of tumor. In addition to be a MRI contrast agent for tumor localization, HSA-SPIO can absorb pulsed microwave energy and transform it into shockwave via the thermoelastic effect. Thereby, the reconstructed TA image by detecting TA signal is expected to be a sensitive and accurate representation of the HSA-SPIO accumulation in tumor. More importantly, owing to the selective retention of HSA-SPIO in tumor tissues and strong TA shockwave at the cellular level, HSA-SPIO induced TA effect under microwave-pulse radiation can be used to highly-efficiently kill cancer cells and inhibit tumor growth. Furthermore, ultra-short pulsed microwave with high excitation efficiency and deep penetrability in biological tissues makes TA therapy a highly-efficient anti-tumor modality on the versatile platform. Overall, HSA-SPIO mediated MRI and TA imaging would offer more comprehensive diagnostic information and enable dynamic visualization of nanoagents in the tumorous tissue thereby tumor-targeted therapy. PMID:28638483

  3. Ultra-short pulse delivery at high average power with low-loss hollow core fibers coupled to TRUMPF's TruMicro laser platforms for industrial applications

    NASA Astrophysics Data System (ADS)

    Baumbach, S.; Pricking, S.; Overbuschmann, J.; Nutsch, S.; Kleinbauer, J.; Gebs, R.; Tan, C.; Scelle, R.; Kahmann, M.; Budnicki, A.; Sutter, D. H.; Killi, A.

    2017-02-01

    Multi-megawatt ultrafast laser systems at micrometer wavelength are commonly used for material processing applications, including ablation, cutting and drilling of various materials or cleaving of display glass with excellent quality. There is a need for flexible and efficient beam guidance, avoiding free space propagation of light between the laser head and the processing unit. Solid core step index fibers are only feasible for delivering laser pulses with peak powers in the kW-regime due to the optical damage threshold in bulk silica. In contrast, hollow core fibers are capable of guiding ultra-short laser pulses with orders of magnitude higher peak powers. This is possible since a micro-structured cladding confines the light within the hollow core and therefore minimizes the spatial overlap between silica and the electro-magnetic field. We report on recent results of single-mode ultra-short pulse delivery over several meters in a lowloss hollow core fiber packaged with industrial connectors. TRUMPF's ultrafast TruMicro laser platforms equipped with advanced temperature control and precisely engineered opto-mechanical components provide excellent position and pointing stability. They are thus perfectly suited for passive coupling of ultra-short laser pulses into hollow core fibers. Neither active beam launching components nor beam trackers are necessary for a reliable beam delivery in a space and cost saving packaging. Long term tests with weeks of stable operation, excellent beam quality and an overall transmission efficiency of above 85 percent even at high average power confirm the reliability for industrial applications.

  4. Transcriptional Dynamics Elicited by a Short Pulse of Notch Activation Involves Feed-Forward Regulation by E(spl)/Hes Genes

    PubMed Central

    Housden, Ben E.; Fu, Audrey Q.; Krejci, Alena; Bernard, Fred; Fischer, Bettina; Tavaré, Simon; Russell, Steven; Bray, Sarah J.

    2013-01-01

    Dynamic activity of signaling pathways, such as Notch, is vital to achieve correct development and homeostasis. However, most studies assess output many hours or days after initiation of signaling, once the outcome has been consolidated. Here we analyze genome-wide changes in transcript levels, binding of the Notch pathway transcription factor, CSL [Suppressor of Hairless, Su(H), in Drosophila], and RNA Polymerase II (Pol II) immediately following a short pulse of Notch stimulation. A total of 154 genes showed significant differential expression (DE) over time, and their expression profiles stratified into 14 clusters based on the timing, magnitude, and direction of DE. E(spl) genes were the most rapidly upregulated, with Su(H), Pol II, and transcript levels increasing within 5–10 minutes. Other genes had a more delayed response, the timing of which was largely unaffected by more prolonged Notch activation. Neither Su(H) binding nor poised Pol II could fully explain the differences between profiles. Instead, our data indicate that regulatory interactions, driven by the early-responding E(spl)bHLH genes, are required. Proposed cross-regulatory relationships were validated in vivo and in cell culture, supporting the view that feed-forward repression by E(spl)bHLH/Hes shapes the response of late-responding genes. Based on these data, we propose a model in which Hes genes are responsible for co-ordinating the Notch response of a wide spectrum of other targets, explaining the critical functions these key regulators play in many developmental and disease contexts. PMID:23300480

  5. Expression of heat shock proteins 70 and 47 in tissues following short-pulse laser irradiation: assessment of thermal damage and healing.

    PubMed

    Sajjadi, Amir Yousef; Mitra, Kunal; Grace, Michael

    2013-10-01

    In order to develop effective laser-based therapeutics, the extent of laser-induced damage must be quantified for given laser parameters. Therefore, we want to determine the spatiotemporal expression patterns of heat shock proteins, both to understand the roles of heat shock proteins in laser-induced tissue damage and repair and to develop heat shock proteins as tools to illustrate the extent of laser-induced damage and wound healing following irradiation. We exposed anesthetized mice to the focused beam of a short-pulse Nd:YAG laser (1064 nm; 200 ns pulsewidth) for 15s, while measuring temperature distribution in the skin using an infrared thermal camera. Following irradiation, we examined expression of HSP47 and HSP70 over time (0-24h) as indicators of the heat shock response and recovery from damage in the laser-irradiated region. Expression patterns of HSP70 and HSP47 as detected by immunohistochemistry and confocal microscopy delineate the extent of damage and the process of healing in tissue. Both HSP70 and HSP47 were expressed in dermis and epidermis following laser irradiation, and the spatial and temporal changes in HSP expression patterns define the laser-induced thermal damage zone and the process of healing in tissues. HSP70 may define biochemically the thermal damage zone in which cells are targeted for destruction, and HSP47 may illustrate the process of recovery from thermally induced damage. Studying the effects of different laser parameters on the expression of HSPs will allow development of effective laser therapies that provide accurate and precise tissue ablation and may promote rapid wound healing following laser-based surgery. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

  6. Atomistic simulation study of short pulse laser interactions with a metal target under conditions of spatial confinement by a transparent overlayer

    NASA Astrophysics Data System (ADS)

    Karim, Eaman T.; Shugaev, Maxim; Wu, Chengping; Lin, Zhibin; Hainsey, Robert F.; Zhigilei, Leonid V.

    2014-05-01

    The distinct characteristics of short pulse laser interactions with a metal target under conditions of spatial confinement by a solid transparent overlayer are investigated in a series of atomistic simulations. The simulations are performed with a computational model combining classical molecular dynamics (MD) technique with a continuum description of the laser excitation, electron-phonon equilibration, and electronic heat transfer based on two-temperature model (TTM). Two methods for incorporation of the description of a transparent overlayer into the TTM-MD model are designed and parameterized for Ag-silica system. The material response to the laser energy deposition is studied for a range of laser fluences that, in the absence of the transparent overlayer, covers the regimes of melting and resolidification, photomechanical spallation, and phase explosion of the overheated surface region. In contrast to the irradiation in vacuum, the spatial confinement by the overlayer facilitates generation of sustained high-temperature and high-pressure conditions near the metal-overlayer interface, suppresses the generation of unloading tensile wave, decreases the maximum depth of melting, and prevents the spallation and explosive disintegration of the surface region of the metal target. At high laser fluences, when the laser excitation brings the surface region of the metal target to supercritical conditions, the confinement prevents the expansion and phase decomposition characteristic for the vacuum conditions leading to a gradual cooling of the hot compressed supercritical fluid down to the liquid phase and eventual solidification. The target modification in this case is limited to the generation of crystal defects and the detachment of the metal target from the overlayer.

  7. The effects of short pulse laser surface cleaning on porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture

    NASA Astrophysics Data System (ADS)

    AlShaer, A. W.; Li, L.; Mistry, A.

    2014-12-01

    Laser welding of aluminium alloys typically results in porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on porosity reduction during laser welding using a filler wire has not been reported before. In this work, porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to reduce porosity significantly in the weld fusion zones. For the fillet edge welds, porosity was reduced to less than 0.5% compared with 10-80% without laser cleaning. For flange couch welds, porosity was reduced to 0.23-0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the porosity formation. The laser cleaning is based on thermal ablation. This research focuses on porosity reduction in laser welding of aluminium alloy. Weld quality was investigated for two joints, fillet edge and flange couch joints. The effect of laser cleaning on porosity reduction after welding was investigated. It was found that laser cleaning reduced porosity less than 1% in both joints. Weld dimensions and strength were evaluated and discussed for both types of joints.

  8. Generation of nanocrystalline surface layer in short pulse laser processing of metal targets under conditions of spatial confinement by solid or liquid overlayer

    NASA Astrophysics Data System (ADS)

    Shugaev, Maxim V.; Shih, Cheng-Yu; Karim, Eaman T.; Wu, Chengping; Zhigilei, Leonid V.

    2017-09-01

    The effect of spatial confinement by a solid or liquid overlayer on short pulse laser-induced surface microstructure modification is investigated in a series of large-scale atomistic simulations performed for Ag targets irradiated in the regime of melting and resolidification, below the thresholds for laser spallation and ablation. For Ag targets with free surfaces, the formation of a nanocrystalline region with random crystallographic grain orientation is observed under irradiation conditions leading to the generation of numerous sub-surface voids that slow down the solidification process. When no voids are generated, the resolidification produces grains misoriented with respect to the bulk of the target by just several degrees and separated from each other by low angle grain boundaries or dislocation walls. The presence of a liquid or solid overlayer suppresses nucleation of sub-surface voids, provides an additional pathway for cooling through the heat conduction to the overlayer, and facilitates the formation of nanocrystalline structure in a region of the metal target adjacent to the overlayer. Moreover, the stabilizing effect of the solid overlayer may result in an incomplete melting of metal in the vicinity of the interface, making it possible for grains growing from the interface to retain ;memory; of the target orientation and to produce nanocrystalline interfacial region with small misorientation of grains with respect to the bulk of the target. In all simulations, the nanocrystalline layers generated by laser processing of single crystal Ag targets are characterized by a high density of stacking faults, twin boundaries, and point defects produced in the course of the rapid resolidification.

  9. High average power, high energy 1.55 μm ultra-short pulse laser beam delivery using large mode area hollow core photonic band-gap fiber.

    PubMed

    Peng, Xiang; Mielke, Michael; Booth, Timothy

    2011-01-17

    We demonstrate high average power, high energy 1.55 μm ultra-short pulse (<1 ps) laser delivery using helium-filled and argon-filled large mode area hollow core photonic band-gap fibers and compare relevant performance parameters. The ultra-short pulse laser beam-with pulse energy higher than 7 μJ and pulse train average power larger than 0.7 W-is output from a 2 m long hollow core fiber with diffraction limited beam quality. We introduce a pulse tuning mechanism of argon-filled hollow core photonic band-gap fiber. We assess the damage threshold of the hollow core photonic band-gap fiber and propose methods to further increase pulse energy and average power handling.

  10. Generation of Subsurface Voids, Incubation Effect, and Formation of Nanoparticles in Short Pulse Laser Interactions with Bulk Metal Targets in Liquid: Molecular Dynamics Study.

    PubMed

    Shih, Cheng-Yu; Shugaev, Maxim V; Wu, Chengping; Zhigilei, Leonid V

    2017-08-03

    The ability of short pulse laser ablation in liquids to produce clean colloidal nanoparticles and unusual surface morphology has been employed in a broad range of practical applications. In this paper, we report the results of large-scale molecular dynamics simulations aimed at revealing the key processes that control the surface morphology and nanoparticle size distributions by pulsed laser ablation in liquids. The simulations of bulk Ag targets irradiated in water are performed with an advanced computational model combining a coarse-grained representation of liquid environment and an atomistic description of laser interaction with metal targets. For the irradiation conditions that correspond to the spallation regime in vacuum, the simulations predict that the water environment can prevent the complete separation of the spalled layer from the target, leading to the formation of large subsurface voids stabilized by rapid cooling and solidification. The subsequent irradiation of the laser-modified surface is found to result in a more efficient ablation and nanoparticle generation, thus suggesting the possibility of the incubation effect in multipulse laser ablation in liquids. The simulations performed at higher laser fluences that correspond to the phase explosion regime in vacuum reveal the accumulation of the ablation plume at the interface with the water environment and the formation of a hot metal layer. The water in contact with the metal layer is brought to the supercritical state and provides an environment suitable for nucleation and growth of small metal nanoparticles from metal atoms emitted from the hot metal layer. The metal layer itself has limited stability and can readily disintegrate into large (tens of nanometers) nanoparticles. The layer disintegration is facilitated by the Rayleigh-Taylor instability of the interface between the higher density metal layer decelerated by the pressure from the lighter supercritical water. The nanoparticles emerging

  11. Generation of Subsurface Voids, Incubation Effect, and Formation of Nanoparticles in Short Pulse Laser Interactions with Bulk Metal Targets in Liquid: Molecular Dynamics Study

    PubMed Central

    2017-01-01

    The ability of short pulse laser ablation in liquids to produce clean colloidal nanoparticles and unusual surface morphology has been employed in a broad range of practical applications. In this paper, we report the results of large-scale molecular dynamics simulations aimed at revealing the key processes that control the surface morphology and nanoparticle size distributions by pulsed laser ablation in liquids. The simulations of bulk Ag targets irradiated in water are performed with an advanced computational model combining a coarse-grained representation of liquid environment and an atomistic description of laser interaction with metal targets. For the irradiation conditions that correspond to the spallation regime in vacuum, the simulations predict that the water environment can prevent the complete separation of the spalled layer from the target, leading to the formation of large subsurface voids stabilized by rapid cooling and solidification. The subsequent irradiation of the laser-modified surface is found to result in a more efficient ablation and nanoparticle generation, thus suggesting the possibility of the incubation effect in multipulse laser ablation in liquids. The simulations performed at higher laser fluences that correspond to the phase explosion regime in vacuum reveal the accumulation of the ablation plume at the interface with the water environment and the formation of a hot metal layer. The water in contact with the metal layer is brought to the supercritical state and provides an environment suitable for nucleation and growth of small metal nanoparticles from metal atoms emitted from the hot metal layer. The metal layer itself has limited stability and can readily disintegrate into large (tens of nanometers) nanoparticles. The layer disintegration is facilitated by the Rayleigh–Taylor instability of the interface between the higher density metal layer decelerated by the pressure from the lighter supercritical water. The nanoparticles

  12. Demonstration of short pulse laser heating of solid targets to temperatures of 600eV at depths exceeding 30μm using the Orion high power laser

    NASA Astrophysics Data System (ADS)

    Hobbs, L. M. R.; Hoarty, D. J.; Allan, P.; Brown, C. R. D.; Hill, M. P.; James, S. F.; Shepherd, R.; Lancaster, K. L.; Gray, R. J.; Wagenaars, E.; Dance, R. J.; Rossall, A. K.; Culfa, O.; Woolsey, N. C.

    2012-10-01

    The recently completed Orion laser at AWE in the UK has the capability of delivering a petaWatt short pulse at 1.06μm in two of its twelve laser beams. In the experiments described one of the short pulse beams was converted to 2nd harmonic at sub-aperture delivering 3x10^20W/cm^2 (100J of 0.53μm light in 0.5ps) onto plastic foils (parylene N) with embedded tracer layers of aluminium. The target heating profile was recorded on a shot by shot basis by changing the depth of the plastic overcoat between the laser and the buried aluminium layer and recording the aluminium K-shell emission spectra. These spectra were then compared to the FLY atomic kinetics and line-shape code to infer the conditions in the target. Temperatures of 600eV were recorded through a plastic depth in excess of 30μm. In contrast to this similar experiments conducted with the Orion short pulse beam operating at wavelength 1.06μm at energy of 500J (˜10^21W/cm^2) produced heating through only 5μm of plastic. The importance of the improved pulse contrast in 2nd harmonic operation in solid target heating is clear from these results. The data are also compared to results from similar experiments conducted on the VULCAN petaWatt laser using 1.06μm light but with improved pulse contrast.

  13. Complex characterization of short-pulse propagation through InAs/InP quantum-dash optical amplifiers: from the quasi-linear to the two-photon-dominated regime.

    PubMed

    Capua, Amir; Saal, Abigael; Karni, Ouri; Eisenstein, Gadi; Reithmaier, Johann Peter; Yvind, Kresten

    2012-01-02

    We describe direct measurements at a high temporal resolution of the changes experienced by the phase and amplitude of an ultra-short pulse upon propagation through an inhomogenously broadened semiconductor nanostructured optical gain medium. Using a cross frequency-resolved optical gating technique, we analyze 150 fs-wide pulses propagating along an InP based quantum dash optical amplifier in both the quasi-linear and saturated regimes. For very large electrical and optical excitations, a second, trailing peak is generated and enhanced by a unique two-photon-induced amplification process.

  14. Emittance of short-pulsed high-current ion beams formed from the plasma of the electron cyclotron resonance discharge sustained by high-power millimeter-wave gyrotron radiation

    NASA Astrophysics Data System (ADS)

    Razin, S.; Zorin, V.; Izotov, I.; Sidorov, A.; Skalyga, V.

    2014-02-01

    We present experimental results on measuring the emittance of short-pulsed (≤100 μs) high-current (80-100 mA) ion beams of heavy gases (Nitrogen, Argon) formed from a dense plasma of an ECR source of multiply charged ions (MCI) with quasi-gas-dynamic mode of plasma confinement in a magnetic trap of simple mirror configuration. The discharge was created by a high-power (90 kW) pulsed radiation of a 37.5-GHz gyrotron. The normalized emittance of generated ion beams of 100 mA current was (1.2-1.3) π mm mrad (70% of ions in the beams). Comparing these results with those obtained using a cusp magnetic trap, it was concluded that the structure of the trap magnetic field lines does not exert a decisive influence on the emittance of ion beams in the gas-dynamic ECR source of MCI.

  15. Comparison of two Q-switched lasers and a short-pulse erbium-doped yttrium aluminum garnet laser for treatment of cosmetic tattoos containing titanium and iron in an animal model.

    PubMed

    Wang, Chia-Chen; Huang, Chuen-Lin; Yang, An-Hang; Chen, Chih-Kang; Lee, Shao-Chen; Leu, Fur-Jiang

    2010-11-01

    Cosmetic tattoos contain titanium and ferric oxide and darken through reduction after Q-switched laser irradiation. The optimal treatment for removing these pigments remains unknown. To compare the effects of two Q-switched lasers and a short-pulse erbium-doped yttrium aluminum garnet (SP Er:YAG) laser to remove cosmetic tattoos in an animal model. Rats were tattooed using white, flesh-colored, and brown inks (4 bands of each color) on their backs. For each color, one band was left untreated, and one each was treated with a Q-switched neodymium-doped YAG laser, a Q-switched alexandrite laser, and a SP Er:YAG laser every 3 weeks until the pigments were clear. The two Q-switched lasers were equally effective; all three pigments darkened initially and then resolved gradually. Up to 20, 18, and 10 sessions were required to remove white, flesh-colored, and brown tattoos, respectively. Only six sessions were required with the SP Er:YAG laser. Minimal scarring was observed with all lasers. Skin biopsies confirmed pigment granule fragmentation after Q-switched laser treatment and a decrease in the amount of pigment after SP Er:YAG laser treatment. The SP Er:YAG laser was superior to the Q-switched lasers for removing cosmetic tattoos. © 2010 by the American Society for Dermatologic Surgery, Inc.

  16. 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.

  17. 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.

  18. 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).

  19. 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.

  20. 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, limiting the extent to which the core diameter can be grown and still ensure single mode operation from the fiber. The large flattened mode fiber addresses some of these limitations and enables a new approach to single transverse mode operation of large mode area (LMA) fibers, providing a route to high average powers exceeding 1 kW from a single aperture in a Strehi-ratio-optimizing fiat-topped output beam.

  1. Short Pulse UV-Visible Waveguide Laser.

    DTIC Science & Technology

    1980-07-01

    millimeters of the capillary tube ends. 7 A perimetric study of the laser operation was conducted in which the gas pressure, gas mixture, applied voltage, gas...removal rate through an increase in the V-T vibrational relaxation rate. When the dye laser was adjusted to the red side of the blue transition

  2. 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.

  3. Bond strength of etch-and-rinse and self-etch adhesive systems to enamel and dentin irradiated with a novel CO2 9.3 μm short-pulsed laser for dental restorative procedures.

    PubMed

    Rechmann, Peter; Bartolome, N; Kinsel, R; Vaderhobli, R; Rechmann, B M T

    2017-08-15

    The objective of this study was to evaluate the influence of CO2 9.3 μm short-pulsed laser irradiation on the shear bond strength of composite resin to enamel and dentin. Two hundred enamel and 210 dentin samples were irradiated with a 9.3 µm carbon dioxide laser (Solea, Convergent Dental, Inc., Natick, MA) with energies which either enhanced caries resistance or were effective for ablation. OptiBond Solo Plus [OptiBondTE] (Kerr Corporation, Orange, CA) and Peak Universal Bond light-cured adhesive [PeakTE] (Ultradent Products, South Jordan, UT) were used. In addition, Scotchbond Universal [ScotchbondSE] (3M ESPE, St. Paul, MN) and Peak SE self-etching primer with Peak Universal Bond light-cured adhesive [PeakSE] (Ultradent Products) were tested. Clearfil APX (Kuraray, New York, NY) was bonded to the samples. After 24 h, a single plane shear bond test was performed. Using the caries preventive setting on enamel resulted in increased shear bond strength for all bonding agents except for self-etch PeakSE. The highest overall bond strength was seen with PeakTE (41.29 ± 6.04 MPa). Etch-and-rinse systems achieved higher bond strength values to ablated enamel than the self-etch systems did. PeakTE showed the highest shear bond strength with 35.22 ± 4.40 MPa. OptiBondTE reached 93.8% of its control value. The self-etch system PeakSE presented significantly lower bond strength. The shear bond strength to dentin ranged between 19.15 ± 3.49 MPa for OptiBondTE and 43.94 ± 6.47 MPa for PeakSE. Etch-and-rinse systems had consistently higher bond strength to CO2 9.3 µm laser-ablated enamel. Using the maximum recommended energy for dentin ablation, the self-etch system PeakSE reached the highest bond strength (43.9 ± 6.5 MPa).

  4. RCS Based Hardware-in-the-Loop Intelligent System Design and Performance Measurement

    DTIC Science & Technology

    2002-08-01

    controller that we choose for the system given by (5) is a PI controller of the form shown in equation (6), namely, ,))()(())()(()( 0 ∫ −+−= t t...noticed. Then, as the ram plunges the cylinder, the nonlinear control is able to track the reference pressure trajectory, while the PI control causes...Reference Low bandwidth valve Mechanical press, simple PI controller Nonlinear Control Simulation for a Mechanical Press PI Control Simulation for a

  5. 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.

  6. 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.

  7. Short Pulse Switches for Airborne High Power Supplies

    DTIC Science & Technology

    1973-10-01

    IB 8. Rotary Mechanical Switch 20 9. Mechanical Switch, Essential Elements 24 10. Motor , Torsion Bar Electrodynamic Drive 28 11. Fast Acting...Gas Valve 31 12. Motor Test, Conductance, and Torque 33 13. Measured Motor Characteristics 34 14. Motor Structural Test Sample 36 15. Motor ...Fig. 42. Fig. 43. Fig. 44. Fig. 45. Fig. 46. Fig. 47. Fig. 48. Mechanical Switch 49 Arcing Contacts 51 Nonarcing Contacts 53 Motor

  8. Short Pulse Switches for Airborne High Power Supplies

    DTIC Science & Technology

    1973-10-01

    must be small and lightweight and must operate reliably for 50.000 cycles. All of these design goals can be met utilizing the vacuum interrupter... reliability and to significantly reduce development and future manufacturing costs. Where necessary, modifications have been made to these components in...Westlnghouse proprietary material utilized In our current vacuum Interrupter product line. In order to Insure highly reliable lightweight actuation of

  9. 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 diamond, forming undesirable grain boundaries and rough surfaces that are difficult to polish. In addition, PLD generated films tend to be ''amorphous'' or nanocrystalline with no observable long-range order, but still possessing physical properties which are diamond-like in some approximation. This has given rise to the term ''diamond-like carbon'' when referring to these PLD-produced, amorphous carbon films. Growth rates for PLD have been prohibitively slow until recently with the advent of high average power, high rep-rate lasers.

  10. The Effect of Short-Pulse Laser Radiation on Coatings

    DTIC Science & Technology

    1975-04-01

    designed to conceal targeta in the visible and near-Infrared spectral regions. If this coating were removed, the probability of being detected would be...appendix to sketch the development of such a calculation. This is certainly not an original proof l»ut is intended solely to refresh the memory of the

  11. Ultra-Short Pulsed Laser Engineered Metal-Glass Nanocomposites

    NASA Astrophysics Data System (ADS)

    Stalmashonak, Andrei; Seifert, Gerhard; Abdolvand, Amin

    Glasses and other dielectrics containing metallic nanoparticles are very promising materials for applications in optoelectronics due to their unique linear and non-linear optical properties. These properties are dominated by the strong surface plasmon resonance (SPR) of the metal nanoparticles. The SPR occurs when the electron and light waves couple with each other at a metal-dielectric interface. These are regarded as the collective oscillation of the nanoparticle (NP) electrons.

  12. Tissue photoablation process with short-pulsed lasers

    NASA Astrophysics Data System (ADS)

    Mueller, Gerhard J.; Doerschel, Klaus; Kar, Hasan

    1992-03-01

    Since Hippocrates, physicians have three weapons to fight malignant diseases of the human body: Quae medicamenta non sanat, ferrum sanat; quae ferrum non sanat, ignis sanat; and quae vero ignis non sanat, insanabilia reputari oportet. Today there are various possibilities to use the ''fire'': electrical and optical cauterization; mono- and bipolar rf-surgery; ionizing radiation for tumor treatment; and last but not least, the laser of laser tissue interactions, all can be used to remove malignant tissue either by biological digestion or immediate ablation, i.e., photovaporization or photodecomposition. This paper will discuss a semiempirical theory of the so-called photoablation process and the thermal side effects of the surrounding tissue. The term ''Photoablation; has to be well differentiated with the terms photovaporization, photodisruption and photofragmentation. As will be shown in this paper, photoablation is a microscale fast thermal explosion.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. Short-pulse duration retinal lasers: a review.

    PubMed

    Chehade, Luke; Chidlow, Glyn; Wood, John; Casson, Robert J

    2016-11-01

    The development of lasers for biological use was an important medical advance in the 20th century with numerous evidence-based therapeutic applications to retinal disease, including capillary leakage at the macula. Although the role of photocoagulative laser in the treatment of macular oedema has diminished, there is evidence for a modified role in clinical management, particularly for extrafoveal leakage. Additionally, it may reduce the frequency of required intravitreal injections and assist in visual stabilization when used as an adjunct. The tissue destructive effect of photocoagulative lasers has motivated the development of safer macular lasers and the search for novel therapeutic applications, including treatment of drusen and regeneration of dysfunctional retinal pigment epithelium.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Propellant sidefeed-short pulse discharge thruster studies

    NASA Technical Reports Server (NTRS)

    Palumbo, D. J.; Guman, W. J.

    1972-01-01

    The technique of feeding a solid propellant into the discharge from the sides of the discharge was evaluated. The thrust/power ratio could be significantly effected by the included angle of V-shaped propellants and by the electrode length. This result implies that when results are compared at the same specific impulse it is possible to obtain higher thrust efficiencies. In particular, it was found that for a given discharge energy the thrust/power ratio correlated with propellant mass. Increasing the integral simultaneously increases both the gas dynamic and electromagnetic thrust. An analytic expression was formulated for ablated mass which comprehensively describes experimental data in terms of geometry and electrical parameters. The correlation of the product impulse x specific impulse with discharge energy was also described. It is suggested that the reliability of dry energy storage capacitors does not equal the reliability of liquid impregnated units when the comparison is made at the same joules/Kg rating.

  4. 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).

  5. Characterization of short-pulse laser driven neutron source

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  6. 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.

  7. 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.

  8. 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.

  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. 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. 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.

  12. 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.

  13. 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.

  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. Picosecond lasers: the next generation of short-pulsed lasers.

    PubMed

    Freedman, Joshua R; Kaufman, Joely; Metelitsa, Andrea I; Green, Jeremy B

    2014-12-01

    Selective photothermolysis, first discussed in the context of targeted microsurgery in 1983, proposed that the optimal parameters for specific thermal damage rely critically on the duration over which energy is delivered to the tissue. At that time, nonspecific thermal damage had been an intrinsic limitation of all commercially available lasers, despite efforts to mitigate this by a variety of compensatory cooling mechanisms. Fifteen years later, experimental picosecond lasers were first reported in the dermatological literature to demonstrate greater efficacy over their nanosecond predecessors in the context of targeted destruction of tattoo ink. Within the last 4 years, more than a decade after those experiments, the first commercially available cutaneous picosecond laser unit became available (Cynosure, Westford, Massachusetts), and several pilot studies have demonstrated its utility in tattoo removal. An experimental picosecond infrared laser has also recently demonstrated a nonthermal tissue ablative capability in soft tissue, bone, and dentin. In this article, we review the published data pertaining to dermatology on picosecond lasers from their initial reports to the present as well as discuss forthcoming technology.

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

    DTIC Science & Technology

    1981-02-01

    DPS-�’ D1IRE𔃻 ’PS A-rN .4N-40’ FE’NI L IP ATTN"l RECl ’ PIj ’VY, 12 MTt AK I’ ’ I’APPNSD H l’!APAPY, 9111m’ (3 -- ’PIES,) APP (’N ir. !IPTRAI<Y

  17. Characterization of short pulse laser-produced plasmas at the Lawrence Livermore National Laboratory ultra short-pulse laser

    SciTech Connect

    Shepherd, R.; Price, D.; White, W.; Osterheld, A.; Walling, R.; Goldstein, W.; Stewart, R.; Gordan, S.

    1993-07-14

    The K-shell emission from porous aluminum targets is used to infer the density and temperature of plasmas created with 800 nm and 400 nm, 140 fs laser light. The laser beam is focused to a minimum spot size of 5 {mu}m with 800 nm light and 3 {mu}m with 400 nm light, producing a normal incidence peak intensity of 10{sup 18} Watts/cm{sup 2}. A new 800 fs x-ray streak camera is used to study the broadband x-ray emission. The time resolved and time integrated x-ray emission implies substantial differences between the porous target and the flat target temperature.

  18. 1.5 MW turbine installation at NREL's NWTC on Aug. 21

    ScienceCinema

    None

    2016-07-12

    Generating 20 percent of the nation's electricity from clean wind resources will require more and bigger wind turbines. NREL is installing two large wind turbines at the National Wind Technology Center to examine some of the industry's largest machines and address issues to expand wind energy on a commercial scale.

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

    NASA Astrophysics Data System (ADS)

    Zheng, Lihe; Taira, Takunori

    2016-03-01

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

  20. Definition of a 5-MW Reference Wind Turbine for Offshore System Development

    SciTech Connect

    Jonkman, J.; Butterfield, S.; Musial, W.; Scott, G.

    2009-02-01

    This report describes a three-bladed, upwind, variable-speed, variable blade-pitch-to-feather-controlled multimegawatt wind turbine model developed by NREL to support concept studies aimed at assessing offshore wind technology.

  1. Cryopump development of the 5 MW neutral beam injector system on HL-2M tokamak

    NASA Astrophysics Data System (ADS)

    Yang, Xianfu; Cao, Jianyong; Liu, He; Wei, Huiling; Liu, Weicheng; Ma, Hong

    2017-07-01

    In order to carry out the long pulse and high power neutral beam injector (NBI) heating experiment on the HL-2M tokamak and satisfy its high vacuum pumping speed in the NBI, two built-in cryopumps with large area and based on a three-stage adsorption structure have been developed. The design idea and size of the three stage structure, the manufacturing technique, and the test experiment for cryopumps have been described in this paper. The experimental result shows that the cooldown time of liquid nitrogen pipes and liquid helium pipes are 1.5 h and 10 min, respectively. With activated charcoal bonded on the condensation plates, the pumping speed reaches 1.13 × 106 l/s, and the consumption of liquid helium is 2.53 g/s and 3.11 g/s for the 4-component pump and the 5-component pump, respectively. The conductance probability of the pump inlet is 0.25 for hydrogen.

  2. Engineering aspects of the application of structural materials in the 5 MW-ESS-mercury-target

    SciTech Connect

    Guttek, B.

    1996-06-01

    A main problem of the ESS-Hg-target development and the design of the components of its primary Hg-circuit is the choice of structural materials. As designing, calculations and experiments with elected materials take time and are very costy, a preview on their successful application has to be done before as detailed as possible. One aspect on this is to have the knowledge of characteristics values of the structural material candidates under the occuring mechanical and thermal loads, irradiation, corrosion and erosion. Another point is the technology of engineering concerning the manufacturing, welding, surface treatment, and quality control of such parts and components under the demand to reach maximum lifetime.

  3. Long-pulse operation of a 0.5 MW TE{sub 10.4} gyrotron at 140 GHz

    SciTech Connect

    Dammertz, G.; Iatrou, C.T.; Kuntze, M.; Moebius, A.; Piosczyk, B.; Braz, O.; Thumm, M. |

    1996-06-01

    Gyrotron oscillators have proven to be highly efficient sources of coherent mm-wave radiation. They have been used successfully for electron cyclotron resonance heating (ECRH) experiments and electron cyclotron diagnostics (ECD) of plasma fusion for some time. Due to the localized energy deposition, the temperature profile can be modified and the stability of the plasma can be improved. Here, the operation features of a TE{sub 10.4}-mode gyrotron oscillator with a quasi-optical mode converter and a single-stage depressed collector at 140 GHz with an output power of 500 kW in long pulses of 0.2 s are presented. Measurements on long-pulse operation of the tube are described in detail, and the significant differences between short- and long-pulse operation concerning efficiency and output power are pointed out. The variation of frequency during a pulse and an irreversible frequency shift during long-pulse operation were measured and are discussed with respect to gyrotron design.

  4. Functional Conceptual Design Criteria - 5-MW/sub e/ salt-gradient solar pond power plant at Great Salt Lake

    SciTech Connect

    Brown, L.M.; Barnhart, J.S.; Cavola, R.G.; Drost, M.K.; Hauser, S.G.; Johnson, B.M.

    1983-08-01

    The purpose of this solar pond plant facility would be to provide valid data on the cost, operation, and reliability of salt-gradient solar ponds as a means of producing power. A general facility description is given which includes design code requirements, site selection, site characteristics, and site-specific design requirements. Functional requirements discussed include: civil-structural; mechanical; electrical; and control, instrumentation and alarms. Occupational and environmental safety, security, and quality assurance are also discussed.

  5. Energy transport in short-pulse-laser-heated targets measured using extreme ultraviolet laser backlighting.

    PubMed

    Wilson, L A; Tallents, G J; Pasley, J; Whittaker, D S; Rose, S J; Guilbaud, O; Cassou, K; Kazamias, S; Daboussi, S; Pittman, M; Delmas, O; Demailly, J; Neveu, O; Ros, D

    2012-08-01

    The accurate characterization of thermal electron transport and the determination of heating by suprathermal electrons in laser driven solid targets are both issues of great importance to the current experiments being performed at the National Ignition Facility, which aims to achieve thermonuclear fusion ignition using lasers. Ionization, induced by electronic heat conduction, can cause the opacity of a material to drop significantly once bound-free photoionization is no longer energetically possible. We show that this drop in opacity enables measurements of the transmission of extreme ultraviolet (EUV) laser pulses at 13.9 nm to act as a signature of the heating of thin (50 nm) iron layers with a 50-nm thick parylene-N (CH) overlay irradiated by 35-fs pulses at irradiance 3×10(16) Wcm(-2). Comparing EUV transmission measurements at different times after irradiation to fluid code simulations shows that the target is instantaneously heated by hot electrons (with approximately 10% of the laser energy), followed by thermal conduction with a flux limiter of ≈0.05.

  6. 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.

  7. 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.

  8. Short-pulse fiber lasers mode-locked by carbon nanotube and graphene

    NASA Astrophysics Data System (ADS)

    Yamashita, Shinji; Set, Sze Y.; Xu, Bo

    2014-09-01

    We review the optical properties of carbon nanotubes (CNTs) and graphene and describe how those properties have been used for the implementation of various nonlinear fiber optic applications. Early studies on the optical properties of CNTs in the late 90s revealed that these materials exhibit high third order susceptibility and a broadband saturable absorption with a sub-picosecond response time. Recent discovery of similar nonlinear optical properties in graphene attracts much attention in this field. Such ultrafast, highly nonlinear optical response means that they can be employed for noise suppression and for the mode-locking of fiber lasers, and in addition, their high third order nonlinearity holds great promise for the implementation of various other nonlinear fiber optic devices such as wavelength converters based on four wave mixing. In this paper, we will discuss the various methods that have been considered thus far for the integration of CNTs and graphene in optical systems and highlight the advantages and limitations of using the saturable absorption of CNTs and graphene for the passive mode-locking of fiber lasers, and the current status of CNT and graphene saturable absorbers in the state of art fiber laser technologies.

  9. Ultrafast electron kinetics in short pulse laser-driven dense hydrogen

    SciTech Connect

    Zastrau, U.; Sperling, P.; Fortmann-Grote, C.; Bornath, T.; Bredow, R.; Doppner, T.; Fennel, T.; Fletcher, L. B.; Forster, E.; Gode, S.; Gregori, G.; Harmand, M.; Hilbert, V.; Laarmann, T.; Lee, H. J.; Ma, T.; Meiwes-Broer, K. H.; Mithen, J. P.; Murphy, C. D.; Nakatsutsumi, M.; Neumayer, P.; Przystawik, A.; Skruszewicz, S.; Tiggesbaumker, J.; Toleikis, S.; White, T. G.; Glenzer, S. H.; Redmer, R.; Tschentscher, T.

    2015-09-25

    Dense cryogenic hydrogen is heated by intense femtosecond infrared laser pulses at intensities of ${10}^{15}-{10}^{16}\\;$ W cm–2. Three-dimensional particle-in-cell (PIC) simulations predict that this heating is limited to the skin depth, causing an inhomogeneously heated outer shell with a cold core and two prominent temperatures of about $25$ and $40\\;\\mathrm{eV}$ for simulated delay times up to $+70\\;\\mathrm{fs}$ after the laser pulse maximum. Experimentally, the time-integrated emitted bremsstrahlung in the spectral range of 8–18 nm was corrected for the wavelength-dependent instrument efficiency. The resulting spectrum cannot be fit with a single temperature bremsstrahlung model, and the best fit is obtained using two temperatures of about 13 and $30\\;$eV. The lower temperatures in the experiment can be explained by missing energy-loss channels in the simulations, as well as the inclusion of hot, non-Maxwellian electrons in the temperature calculation. In conclusion, we resolved the time-scale for laser-heating of hydrogen, and PIC results for laser–matter interaction were successfully tested against the experiment data.

  10. 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.

  11. Novel Laser-Based Hyper-Short Pulse Sources and Single Particle Devices

    DTIC Science & Technology

    2006-05-08

    DISTRIBUTION AVAILABILITY STATEMENT DISTRIBUTION A. Approved for public release; distribution unlimited. 13. SUPPLEMENTARY NOTES 14...Enter report number as assigned by the sponsoring/ monitoring agency, if available, e.g. BRL-TR-829; -215. 12. DISTRIBUTION /AVAILABILITY...STATEMENT. Use agency-mandated availability statements to indicate the public availability or distribution limitations of the report. If additional

  12. Engineering studies related to geodetic and oceanographic remote sensing using short pulse techniques

    NASA Technical Reports Server (NTRS)

    Miller, L. S.; Brown, G. S.; Hayne, G. S.

    1973-01-01

    For the Skylab S-193 radar altimeter, data processing flow charts and identification of calibration requirements and problem areas for defined S-193 altimeter experiments are presented. An analysis and simulation of the relationship between one particular S-193 measurement and the parameter of interest for determining the sea surface scattering cross-section are considered. For the GEOS-C radar altimeter, results are presented for system analyses pertaining to signal-to-noise ratio, pulse compression threshold behavior, altimeter measurement variance characteristics, desirability of onboard averaging, tracker bandwidth considerations, and statistical character of the altimeter data in relation to harmonic analysis properties of the geodetic signal.

  13. Short pulse laser stretcher-compressor using a single common reflective grating

    DOEpatents

    Erbert, Gaylen V.; Biswal, Subrat; Bartolick, Joseph M.; Stuart, Brent C.; Telford, Steve

    2004-05-25

    The present invention provides an easily aligned, all-reflective, aberration-free pulse stretcher-compressor in a compact geometry. The stretcher-compressor device is a reflective multi-layer dielectric that can be utilized for high power chirped-pulse amplification material processing applications. A reflective grating element of the device is constructed: 1) to receive a beam for stretching of laser pulses in a beam stretcher beam path and 2) to also receive stretched amplified pulses to be compressed in a compressor beam path through the same (i.e., common) reflective multilayer dielectric diffraction grating. The stretched and compressed pulses are interleaved about the grating element to provide the desired number of passes in each respective beam path in order to achieve the desired results.

  14. Ultrafast electron kinetics in short pulse laser-driven dense hydrogen

    DOE PAGES

    Zastrau, U.; Sperling, P.; Fortmann-Grote, C.; ...

    2015-09-25

    Dense cryogenic hydrogen is heated by intense femtosecond infrared laser pulses at intensities ofmore » $${10}^{15}-{10}^{16}\\;$$ W cm–2. Three-dimensional particle-in-cell (PIC) simulations predict that this heating is limited to the skin depth, causing an inhomogeneously heated outer shell with a cold core and two prominent temperatures of about $25$ and $$40\\;\\mathrm{eV}$$ for simulated delay times up to $$+70\\;\\mathrm{fs}$$ after the laser pulse maximum. Experimentally, the time-integrated emitted bremsstrahlung in the spectral range of 8–18 nm was corrected for the wavelength-dependent instrument efficiency. The resulting spectrum cannot be fit with a single temperature bremsstrahlung model, and the best fit is obtained using two temperatures of about 13 and $$30\\;$$eV. The lower temperatures in the experiment can be explained by missing energy-loss channels in the simulations, as well as the inclusion of hot, non-Maxwellian electrons in the temperature calculation. In conclusion, we resolved the time-scale for laser-heating of hydrogen, and PIC results for laser–matter interaction were successfully tested against the experiment data.« less

  15. Bilayer Bismuth Selenide nanoplatelets based saturable absorber for ultra-short pulse generation (Invited)

    NASA Astrophysics Data System (ADS)

    Xu, Yanhua; Xie, Hanhan; Jiang, Guobao; Miao, Lili; Wang, Ke; Tang, Siying; Yu, Xuefeng; Zhang, Han; Bao, Qiaoliang

    2017-07-01

    Based on an efficient and bottom-up synthesis technique, Bismuth Selenide (Bi2Se3) nanoplatelets with uniform morphology and average thickness down to 3-7 nm had been fabricated. Its nonlinear absorption property under high power excitation had been well characterized by our Z-scan measurement system at different illumination wavelengths, and we found that the as-fabricated bi-layer Bi2Se3 nanoplatelets show unique nonlinear optical responses, that is, with a saturable optical intensity of 32 GW/cm2 (resp. 3.7 MW/cm2) and a modulation depth of 88% (resp. 36%) at 800 nm (resp. 1565 nm). By implementing its saturable absorption property, we designed an optical saturable absorber device based on bilayer Bi2Se3 nanoplatelets through deposited them onto the end-facet of optical fiber. The as-fabricated optical saturable absorber device allows for the generation of mode-locking pulses at 1571 nm with pulse duration of 579 fs and a repetition rate of 12.54 MHz at a pump power of 160 mW. The method on fabricating ultrathin Bi2Se3 nanoplatelets may pave a new way to massive production of large-area topological insulator thin films that can be used in two-dimensional layered materials related photonics device.

  16. ELI-beamlines: progress in development of next generation short-pulse laser systems

    NASA Astrophysics Data System (ADS)

    Rus, B.; Bakule, P.; Kramer, D.; Naylon, J.; Thoma, J.; Fibrich, M.; Green, J. T.; Lagron, J. C.; Antipenkov, R.; Bartoníček, J.; Batysta, F.; Baše, R.; Boge, R.; Buck, S.; Cupal, J.; Drouin, M. A.; Durák, M.; Himmel, B.; Havlíček, T.; Homer, P.; Honsa, A.; Horáček, M.; Hríbek, P.; Hubáček, J.; Hubka, Z.; Kalinchenko, G.; Kasl, K.; Indra, L.; Korous, P.; Košelja, M.; Koubíková, L.; Laub, M.; Mazanec, T.; Meadows, A.; Novák, J.; Peceli, D.; Polan, J.; Snopek, D.; Šobr, V.; Trojek, P.; Tykalewicz, B.; Velpula, P.; Verhagen, E.; Vyhlídka, Å.; Weiss, J.; Haefner, C.; Bayramian, A.; Betts, S.; Erlandson, A.; Jarboe, J.; Johnson, G.; Horner, J.; Kim, D.; Koh, E.; Marshall, C.; Mason, D.; Sistrunk, E.; Smith, D.; Spinka, T.; Stanley, J.; Stolz, C.; Suratwala, T.; Telford, S.; Ditmire, T.; Gaul, E.; Donovan, M.; Frederickson, C.; Friedman, G.; Hammond, D.; Hidinger, D.; Chériaux, G.; Jochmann, A.; Kepler, M.; Malato, C.; Martinez, M.; Metzger, T.; Schultze, M.; Mason, P.; Ertel, K.; Lintern, A.; Edwards, C.; Hernandez-Gomez, C.; Collier, J.

    2017-05-01

    Overview of progress in construction and testing of the laser systems of ELI-Beamlines, accomplished since 2015, is presented. Good progress has been achieved in construction of all four lasers based largely on the technology of diode-pumped solid state lasers (DPSSL). The first part of the L1 laser, designed to provide 200 mJ <15 fs pulses at 1 kHz repetition rate, is up and running. The L2 is a development line employing a 10 J / 10 Hz cryogenic gas-cooled pump laser which has recently been equipped with an advanced cryogenic engine. Operation of the L3-HAPLS system, using a gas-cooled DPSSL pump laser and a Ti:sapphire broadband amplifier, was recently demonstrated at 16 J / 28 fs, at 3.33 Hz rep rate. Finally, the 5 Hz OPCPA front end of the L4 kJ laser is up running and amplification in the Nd:glass large-aperture power amplifiers was demonstrated.

  17. 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.

  18. Large-Area Short-Pulse Surface Discharges for Laser Excitation.

    DTIC Science & Technology

    1984-01-01

    V. M. Borisov, F. I. Vysikaylo, and 0. B. Khristoforov , High Temp. 21, 635 (1983) [Teplofiz. Vys. Temp. 1, 844 (1983...Tarasenko, and A. I. Fedorov, Soy. Phys. Tech. Phys. ?a, 704 (1980). * 22. V. Yu. Baranov, V. M. Borisov, A. M. Davidovskii, and 0. B. Khristoforov ...Soy. J. Quan- tum Electron. ii, 42 (1981). 23. V. Yu. Baranov, V. M. Borisov, and 0. B. Khristoforov , Soy. J. Quantum Electron. ii, 93 (1981). 24. A

  19. 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.

  20. Feasibility of Thin Fresnel Lens Use in Multi-kj, Short Pulse Laser Systems

    SciTech Connect

    Jovanovic, I; Dixit, S N; Wattellier, B; Hermann, M R; Barty, C P J

    2002-11-18

    Recently-developed, thin-Fresnel-lens technology offers the potential for transmissive focusing of high-peak-power, ultrashort-duration laser pulses. Calculations of the transverse and longitudinal spectral blurring effects of thin Fresnel lenses when used to focus ultrashort, high-energy laser pulses are presented.

  1. 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.

  2. Coherent excitation of a two-state system by a train of short pulses

    NASA Astrophysics Data System (ADS)

    Vitanov, Nikolay V.; Knight, Peter L.

    1995-09-01

    A theoretical nonperturbative study of the coherent excitation of a two-state system by N consecutive equally spaced identical pulses is presented. General relations between the evolution matrix elements in the cases of one and N pulses are obtained in a closed form. For pulse envelopes allowing analytical solutions, these relations enable analytical treatment of pulse-train excitation; for pulses that can only be treated numerically, they shorten the computations by a factor of N. The relations show that the multiple-pulse excitation of a two-state system can be considered as a quantum analog of the diffraction grating. The interaction dynamics substantially depends on the way the train is produced because the phase shift that is accumulated by the probability amplitudes due to the free evolution of the system during and between the pulses differs. In the limit of weak excitation, the results recover earlier conclusions based on perturbative treatments. Simple formulas are derived for the conditions for complete population inversion (CPI) and complete population return (CPR), which differ from the single-pulse ones. These general results are applied to four particular cases that allow analytical solutions: resonant, rectangular, Rosen-Zener, and Allen-Eberly pulses. A common feature in all these cases is that the number and the amplitude of oscillations in the state populations increase with the number of pulses, while their width decreases. For rectangular pulses, CPI is possible below a given value of the ratio between the detuning and the pulse area; this value increases nearly linearly with the number of pulses. For the Rosen-Zener model, CPI is found to be possible for two and more pulses, while it is impossible for a single non-resonant pulse. It is shown that for a given number of pulses there is an upper limit on the detuning for which CPI can be observed; this limit increases logarithmically with the number of pulses. For the Allen-Eberly model, CPR is established to be possible for more than one pulse, while it is impossible for a single pulse. The cases of even and odd number of pulses are shown to lead to substantially different results. The limitations imposed on the detuning by the conditions for CPR and CPI are derived and discussed.

  3. Challenges of dosimetry of ultra-short pulsed very high energy electron beams.

    PubMed

    Subiel, Anna; Moskvin, Vadim; Welsh, Gregor H; Cipiccia, Silvia; Reboredo, David; DesRosiers, Colleen; Jaroszynski, Dino A

    2017-05-11

    Very high energy electrons (VHEE) in the range from 100 to 250MeV have the potential of becoming an alternative modality in radiotherapy because of their improved dosimetric properties compared with 6-20MV photons generated by clinical linear accelerators (LINACs). VHEE beams have characteristics unlike any other beams currently used for radiotherapy: femtosecond to picosecond duration electron bunches, which leads to very high dose per pulse, and energies that exceed that currently used in clinical applications. Dosimetry with conventional online detectors, such as ionization chambers or diodes, is a challenge due to non-negligible ion recombination effects taking place in the sensitive volumes of these detectors. FLUKA and Geant4 Monte Carlo (MC) codes have been employed to study the temporal and spectral evolution of ultrashort VHEE beams in a water phantom. These results are complemented by ion recombination measurements employing an IBA CC04 ionization chamber for a 165MeV VHEE beam. For comparison, ion recombination has also been measured using the same chamber with a conventional 20MeV electron beam. This work demonstrates that the IBA CC04 ionization chamber exhibits significant ion recombination and is therefore not suitable for dosimetry of ultrashort pulsed VHEE beams applying conventional correction factors. Further study is required to investigate the applicability of ion chambers in VHEE dosimetry. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  4. 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.

  5. Ion Acceleration from Pure Frozen Gas Targets using Short Pulse Lasers

    NASA Astrophysics Data System (ADS)

    McCary, Edward; Stehr, Florian; O'Shea, Finn; Jiao, Xuejing; Agustsson, Ronald; Berry, Robert; Chao, Dennis; Gautier, Donald; Letzring, Samuel; Quevedo, Hernan; Woods, Kaley; Hegelich, Bjorn

    2014-10-01

    A system for shooting interchangeable frozen gas ice targets was developed and tested on the Trident laser system at Los Alamos National Lab. A target holder which could hold up to five substrates used for target growing was cryogenically cooled to temperatures below 14 K. The target substrates consisted of holes with diameters ranging from 15 μm-500 μm and TEM grids with micron scale spacing, across which films of ice were frozen by releasing small amounts of pure gas molecules directly into the vacuum target chamber. The thickness of the ice targets was determined by using alpha spectroscopy. Accelerated ion spectra were characterized using a Thomson Parabola with magnetic field strength of 0.92 T and electric field strength of 30kV and radio-chromic film stacks. Hydrogen targets were additionally characterized using stacks of copper which became activated upon exposure to energetic protons resulting in a beta decay signal. The beta decay was imaged on electron sensitive imaging plates to provide an energy spectrum and spacial profile of the proton beam. Results of the interchangeable, laser-based ion accelerator will be presented. Work Supported by NIH grant.

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

    DTIC Science & Technology

    2004-06-01

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

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. Selective laser melting of metal micropowders with short-pulse laser

    NASA Astrophysics Data System (ADS)

    Wałpuski, B.

    2016-09-01

    Selective laser melting is a unique additive technique which can manufacture solid metal objects but it require expensive, high power lasers. The primary aim of this work was to check is it possible to carry out this process by using lower power and high energy pulse laser. The secondary goal was to examine the influence of main technological parameters of selective laser melting on the quality and the thickness of produced layer. The requirements of metal powder, which allowed to obtain a layer with microthickness, were developed.

  12. 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.

  13. Energy coupling in short pulse laser solid interactions and its impact for space debris removal.

    PubMed

    Neely, David; Allott, Ric; Bingham, Bob; Collier, John; Greenhalgh, Justin; Michaelis, Max; Phillips, Jonathan; Phipps, Claude R; McKenna, Paul

    2014-11-01

    Significant advances have been made over the last decade to improve the performance, efficiency, and contrast of high peak and average power laser systems, driven by their use in a wide variety of fields, from the industrial to the scientific. As the contrast of the lasers has improved, interactions with contrasts of 1012 are now routinely undertaken. At such high contrasts, there is negligible preplasma formation and the ionized surface layer created by subpicosecond-duration pulses typically forms a highly reflective "plasma mirror" capable of reflecting between 70% and 90% of the incident energy. Although such interactions are of significant interest for applications such as harmonic source production and to enable the underlying physics to be studied, their low absorption can limit their usefulness for applications such as space debris removal.

  14. The physical response of soft musculoskeletal tissues to short-pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Dark, Marta Lyselle

    An experimental study was performed to determine the physical properties of knee meniscus using a low energy laser technique. Following irradiation by a 10 ns laser pulse, tissue undergoes thermoelastic expansion in response to laser-induced stresses. The stresses evolve, propagating through the tissue. If they exceed the material's strength, ablation occurs-the material ruptures. Below ablation threshold, the material remains in an expanded state until thermal relaxation occurs. We use numerical methods to solve the 3-D thermoelastic wave equation for a hydrated sample. In addition to thermoelastic expansion, expansion due to the formation of cavitation bubbles within the tissue was modeled. Cavitation occurs when tensile stresses rupture fluid. The laser-induced response of a gelatin phantom was measured with a Michelson interferometer and compared with predictions. Using gelatin as a tissue model provided a consistent experimental model of meniscus. Meniscus, like all biological tissue, is highly heterogeneous. By adapting the time dependent numerical solution of the wave equation, the measurement of physical properties of a hydrated sample became possible. The thermoelastic model depends on sound speed, Poisson's ratio, thermal expansion coefficient, and optical penetration depth. Once the behavior of gelatin was understood, human knee meniscus was studied. The thermoelastic model and experiment, allows measurement of physical properties of meniscus. Also, a numerical model of cavitation based on Rayleigh's equations was developed. By comparing experiment and theory in menicus and water, we determined properties important to cavitation: threshold pressure, bubble density, surface tension and nucleation size. Finally, histology was compared with experiment. The presence and amount of cavitation displacement was correlated with the condition of meniscus. Physical properties can be used to diagnose degenerative cartilage. This research has increased understanding of the interaction of short laser pulses with cartilage tissue, and measured significant physical properties of knee meniscus with a minimally invasive laser technique. (Copies available exclusively from MIT Libraries, Rm. 14- 0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  16. 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.

  17. Wavelength and Intensity Dependence of Short Pulse Laser Xenon Double Ionization between 500 and 2300 nm

    NASA Astrophysics Data System (ADS)

    Gingras, G.; Tripathi, A.; Witzel, B.

    2009-10-01

    The wavelength and intensity dependence of xenon ionization with 50 fs laser pulses has been studied using time-of-flight mass spectrometry. We compare the ion yield distribution of singly and doubly charged xenon with the Perelomov-Popov-Terent’ev (PPT) theory, Perelomov, Popov, and Terent’ev, Zh. Eksp. Teor. Fiz.ZETFA70044-4510 50, 1393 (1966) PerelomovPopovTerent’ev[Sov. Phys. JETPSPHJAR0038-5646 23, 924 (1966)], in the regime between 500 and 2300 nm. The intensity dependence for each wavelength is measured in a range between 1×1013 and 1×1015W/cm2. The Xe+-ion signal is in good agreement with the PPT theory at all used wavelengths. In addition we demonstrate that ionic 5s5p6 S2 state is excited by an electron impact excitation process and contributes to the nonsequential double ionization process.

  18. Wavelength and intensity dependence of short pulse laser xenon double ionization between 500 and 2300 nm.

    PubMed

    Gingras, G; Tripathi, A; Witzel, B

    2009-10-23

    The wavelength and intensity dependence of xenon ionization with 50 fs laser pulses has been studied using time-of-flight mass spectrometry. We compare the ion yield distribution of singly and doubly charged xenon with the Perelomov-Popov-Terent'ev (PPT) theory, Perelomov, Popov, and Terent'ev, Zh. Eksp. Teor. Fiz. 50, 1393 (1966) [Sov. Phys. JETP 23, 924 (1966)], in the regime between 500 and 2300 nm. The intensity dependence for each wavelength is measured in a range between 1 x 10(13) and 1 x 10(15) W/cm2. The Xe+-ion signal is in good agreement with the PPT theory at all used wavelengths. In addition we demonstrate that ionic 5s5p6 2S state is excited by an electron impact excitation process and contributes to the nonsequential double ionization process.

  19. 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.

  20. Satellite and Opacity Effects on Resonance Line Shapes Produced from Short-Pulse Laser Heated Foils

    SciTech Connect

    Shepherd, R; Audebert, P; Chen, H-K; Fournier, K B; Peyreusse, O; Moon, S; Lee, R W; Price, D; Klein, L; Gauthier, J C; Springer, P

    2002-12-03

    We measure the He-like, time-resolved emission from thin foils consisting of 250 {angstrom} of carbon-250 {angstrom} of aluminum and 500 {angstrom} aluminum illuminated with a 150 fs laser pulse at an intensity of 1 x 10{sup 19} W/cm{sup 2}. Dielectronic satellite contributions to the 1s{sup 2}-1s2p({sup 1}P), 1s{sup 2}-1s3p({sup 1}P), and 1s{sup 2}1s4p({sup 1}P) line intensities are modeled using the configuration averaged code AVERROES and is found to be significant for all three resonance lines. The contribution of opacity broadening is inferred from the data and found to be significant only in the 1s{sup 2}-1s2p({sup 1}P).

  1. 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.

  2. Manipulating mammalian cell by phase transformed titanium surface fabricated through ultra-short pulsed laser synthesis.

    PubMed

    Chinnakkannu Vijayakumar, Sivaprasad; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-15

    Developing cell sensitive indicators on interacting substrates that allows specific cell manipulation by a combination of physical, chemical or mechanical cues is a challenge for current biomaterials. Hence, various fabrication approaches have been created on a variety of substrates to mimic or create cell specific cues. However, to achieve cell specific cues a multistep process or a post-chemical treatment is often necessitated. So, a simple approach without any chemical or biological treatment would go a long way in developing bio-functionalized substrates to effectively modulate cell adhesion and interaction. The present investigation is aimed to study the manipulative activity induced by phase transformed titanium surface. An ultra-short laser is used to fabricate the phase transformed titanium surface where a polymorphic titanium oxide phases with titanium monoxide (TiO), tri-titanium oxide (Ti3O) and titanium dioxide (TiO2) have been synthesized on commercially pure titanium. Control over oxide phase transformed area was demonstrated via a combination of laser scanning time (laser pulse interaction time) and laser pulse widths (laser pulse to pulse separation time). The interaction of phase transformed titanium surface with NIH3T3 fibroblasts and MC3T3-E1 osteoblast cells developed a new bio-functionalized platforms on titanium based biomaterials to modulate cell migration and adhesion. The synthesized phase transformed titanium surface on the whole appeared to induce directional cues for cell migration with unique preferential cell adhesion unseen by other fabrication approaches. The precise bio-functionalization controllability exhibited during fabrication offers perceptible edge for developing a variety of smart bio-medical devices, implants and cardiovascular stents where the need in supressing specific cell adhesion and proliferation is of great demand.

  3. 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.

  4. Decoration of silica nanowires with gold nanoparticles through ultra-short pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Gontad, F.; Caricato, A. P.; Cesaria, M.; Resta, V.; Taurino, A.; Colombelli, A.; Leo, C.; Klini, A.; Manousaki, A.; Convertino, A.; Rella, R.; Martino, M.; Perrone, A.

    2017-10-01

    The ablation of a metal target at laser energy densities in the range of 1-10 TW/cm2 leads to the generation of nanoparticles (NP) of the ablated material. This aspect is of particular interest if the immobilization of NPs on three-dimensional (3D) substrates is necessary as for example in sensing applications. In this work the deposition of Au NP by irradiation of a Au bulk target with a sub-picosecond laser beam (500 fs; 248 nm; 10 Hz) on 2D (silica and Si(100)) and 3D substrates (silica nanowire forests) is reported for different number of laser pulses (500, 1000, 1500, 2000, 2500). A uniform coverage of small Au NPs (with a diameter of few nm) on both kinds of substrates has been obtained using a suitable number of laser pulses. The presence of spherical droplets, with a diameter ranging from tens of nm up to few μm was also detected on the substrate surface and their presence can be explained by the weak electron-phonon coupling of Au. The optical characterization of the samples on 2D and 3D substrates evidenced the surface plasmon resonance peak characteristic of the Au NPs although further improvements of the size-distribution are necessary for future applications in sensing devices.

  5. An ultra short pulse reconstruction software applied to the GEMINI high power laser system

    NASA Astrophysics Data System (ADS)

    Galletti, Mario; Galimberti, Marco; Hooker, Chris; Chekhlov, Oleg; Tang, Yunxin; Bisesto, Fabrizio Giuseppe; Curcio, Alessandro; Anania, Maria Pia; Giulietti, Danilo

    2016-09-01

    The GRENOUILLE traces of Gemini pulses (15 J, 30 fs, PW, shot per 20 s) were acquired in the Gemini Target Area PetaWatt at the Central Laser Facility (CLF), Rutherford Appleton Laboratory (RAL). A comparison between the characterizations of the laser pulse parameters made using two different types of algorithms: Video Frog and GRenouille/FrOG (GROG), was made. The temporal and spectral parameters came out to be in great agreement for the two kinds of algorithms. In this experimental campaign it has been showed how GROG, the developed algorithm, works as well as VideoFrog algorithm with the PetaWatt pulse class.

  6. 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

  7. Particle characteristics of different materials after ultra-short pulsed laser (USPL) irradiation

    NASA Astrophysics Data System (ADS)

    Meister, Joerg; Schelle, Florian; Kowalczyk, Philip; Frentzen, Matthias

    2012-01-01

    The exposition of nanoparticles caused by laser application in dental health care is an open discussion. Based on the fact that nanoparticles can penetrate through the mucosa, the knowledge about particle characteristics after irradiation with an USPL is of high importance. Therefore, the aim of this study was to investigate the particle characteristics, especially the size of the ablated debris after USPL irradiation. The irradiation was carried out with an USP Nd:YVO4 laser with a center wavelength of 1064 nm. Based on the pulse duration of 8 ps and a pulse repetition rate of 500 kHz the laser emits an average power of 9 W. The materials investigated were dental tissues and dental restorative materials (composite and amalgam), ceramic and different metals (gold and aluminium). The samples were irradiated with a power density in the order of 300 GW/cm2 at distances of 5, 10, 15, and 20 mm. The debris was collected on an object plate. SEM pictures were used for analysis of the ablation debris. Depending on the irradiated material, we observed different kinds of structures: vitreous, flocculent, and pellet-like. The mean particle sizes were 10 x 10 up to 30 x 30 μm2. In addition, a cluster of ablated matter (nanometer range) distributed over the whole irradiated area was found. With increasing distances the cluster structure reduced from multi-layer to mono-layer clusters. Particle sizes in the micrometer and nanometer range were found after irradiation with an USPL. The nanoparticles create a cluster structure which is influenced by increasing distances.

  8. Time-resolved microscopy using variable probe wavelengths for ultra-short pulse interaction (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Bergner, Klaus; Kumkar, Malte; Tünnermann, Andreas; Nolte, Stefan; Seyfarth, Brian

    2017-03-01

    Glass processing with ultrashort laser pulses allow for different material modifications, ranging from smooth refractive index changes which can be used for the generation of waveguides up to large disruptions due to accumulates stress for glass separation. These disruptions, generated by a dense electron plasma, are favored for glass dicing applications. To tailor the resulting material response a fundamental understanding of the laser/material interaction is of interest. Therefore, we analyze the spatio-temporal evolution of free carriers induced by ultrashort laser pulses using a pump-probe setup with high temporal and spatial resolution and various probe wavelengths. Single laser pulses with 1026nm wavelength, 6ps (FWHM) pulse duration and 200μJ pulse energy were applied to fused silica, Borofloat 33 and Gorilla glass. Electron densities around 1 x 1020cm-3 in the focal plane and 1 x 1019cm-3 in front of the focus are obtained, independent from the glass type used. The free carriers slowly decay within several ns, while the decay time depends on both the maximum electron densities reached and glass species. In this process a part of the excited electrons relax within several 10ps into a long-living stage where a transient effect is observed. Here, various probe wavelengths show differences in the recorded signal. A further carrier relaxation leads to permanent (stress, voids) and non-stable (color center) modifications crucial for precise glass dicing applications.

  9. Generation of fluorescent CdSe nanocrystals by short-pulse laser fragmentation

    NASA Astrophysics Data System (ADS)

    Zholudov, Yu. T.; Sajti, C. L.; Slipchenko, N. N.; Chichkov, B. N.

    2015-12-01

    A simple liquid-phase laser fragmentation approach, resulting in the rapid transformation of CdSe microcrystals into colloidal quantum dots (QDs), is presented. Laser fragmentation is achieved by irradiating a CdSe suspension in dimethylformamide with intense infrared, picosecond laser pulses followed by surface passivation with oleylamine or different types of phosphines. The generated QDs reveal perfect colloidal stability preventing agglomeration and precipitation, and show characteristic QD absorption and fluorescence characteristics, whereas their emission properties strongly depend on the surface states and applied capping ligands. These QDs show distinct photoemission under 405-nm single-photon and 800-nm multi-photon excitations in the 560- to 610-nm spectral region corresponding to the QDs size of about 1.5-2 nm in diameter which is confirmed by transmission electron microscopy.

  10. Ultrafast electron kinetics in short pulse laser-driven dense hydrogen

    NASA Astrophysics Data System (ADS)

    Zastrau, U.; Sperling, P.; Fortmann-Grote, C.; Becker, A.; Bornath, T.; Bredow, R.; Döppner, T.; Fennel, T.; Fletcher, L. B.; Förster, E.; Göde, S.; Gregori, G.; Harmand, M.; Hilbert, V.; Laarmann, T.; Lee, H. J.; Ma, T.; Meiwes-Broer, K. H.; Mithen, J. P.; Murphy, C. D.; Nakatsutsumi, M.; Neumayer, P.; Przystawik, A.; Skruszewicz, S.; Tiggesbäumker, J.; Toleikis, S.; White, T. G.; Glenzer, S. H.; Redmer, R.; Tschentscher, T.

    2015-11-01

    Dense cryogenic hydrogen is heated by intense femtosecond infrared laser pulses at intensities of {10}15-{10}16 W cm-2. Three-dimensional particle-in-cell (PIC) simulations predict that this heating is limited to the skin depth, causing an inhomogeneously heated outer shell with a cold core and two prominent temperatures of about 25 and 40 {eV} for simulated delay times up to +70 {fs} after the laser pulse maximum. Experimentally, the time-integrated emitted bremsstrahlung in the spectral range of 8-18 nm was corrected for the wavelength-dependent instrument efficiency. The resulting spectrum cannot be fit with a single temperature bremsstrahlung model, and the best fit is obtained using two temperatures of about 13 and 30 eV. The lower temperatures in the experiment can be explained by missing energy-loss channels in the simulations, as well as the inclusion of hot, non-Maxwellian electrons in the temperature calculation. We resolved the time-scale for laser-heating of hydrogen, and PIC results for laser-matter interaction were successfully tested against the experiment data.

  11. 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.

  12. 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.

  13. Analysis of short pulse laser altimetry data obtained over horizontal path

    NASA Technical Reports Server (NTRS)

    Im, K. E.; Tsai, B. M.; Gardner, C. S.

    1983-01-01

    Recent pulsed measurements of atmospheric delay obtained by ranging to the more realistic targets including a simulated ocean target and an extended plate target are discussed. These measurements are used to estimate the expected timing accuracy of a correlation receiver system. The experimental work was conducted using a pulsed two color laser altimeter.

  14. Engineering studies related to geodetic and oceanographic remote sensing using short pulsed techniques. [using laser probe

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Theoretical basis is presented for a feasibility study of measuring global ocean surface current pattern from satellites and aircraft. The analysis is supported by some preliminary laboratory experiments. Since the ultimate goal is to establish an operational routine for monitoring the global current pattern, a nondisturbing remote sensing device using a laser probe was developed. Detailed construction of the measuring system and the results of some preliminary observations are also presented.

  15. 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 which appear when using a lightpipe in a laser illuminator design.

  16. Enhanced proton beam collimation in the ultra-intense short pulse regime

    NASA Astrophysics Data System (ADS)

    Green, J. S.; Dover, N. P.; Borghesi, M.; Brenner, C. M.; Cameron, F. H.; Carroll, D. C.; Foster, P. S.; Gallegos, P.; Gregori, G.; McKenna, P.; Murphy, C. D.; Najmudin, Z.; Palmer, C. A. J.; Prasad, R.; Romagnani, L.; Quinn, K. E.; Schreiber, J.; Streeter, M. J. V.; Ter-Avetisyan, S.; Tresca, O.; Zepf, M.; Neely, D.

    2014-08-01

    The collimation of proton beams accelerated during ultra-intense laser irradiation of thin aluminum foils was measured experimentally whilst varying laser contrast. Increasing the laser contrast using a double plasma mirror system resulted in a marked decrease in proton beam divergence (20° to <10°), and the enhanced collimation persisted over a wide range of target thicknesses (50 nm-6 µm), with an increased flux towards thinner targets. Supported by numerical simulation, the larger beam divergence at low contrast is attributed to the presence of a significant plasma scale length on the target front surface. This alters the fast electron generation and injection into the target, affecting the resultant sheath distribution and dynamics at the rear target surface. This result demonstrates that careful control of the laser contrast will be important for future laser-driven ion applications in which control of beam divergence is crucial.

  17. 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.

  18. Raman Based Dispersive Systems for Short Pulse Generation and Optical Signal Processing

    NASA Astrophysics Data System (ADS)

    Kalyoncu, Salih Kagan

    Spatiotemporal dispersive systems have been widely utilized for nonlinear optics and optical signal processing applications. This thesis is dedicated to the investigation of dispersive and nonlinear properties of optical fibers, temporal dispersion for real time operation and spatially dispersed pulse shaping systems. In particular, this thesis is focused on Raman based dispersive systems based on such promising techniques as dispersion management, photonic time stretching and space-to-wavelength mapping for synchronous pulse generation and all-optical RF arbitrary waveform generation incorporated with mature MEMS technology. The first part of this thesis discusses a novel technique of using dispersion managed system for synchronous first and second order pulsed Raman lasers that can achieve frequency spacing of up to 1000 cm-1, which are widely utilized for CARS microscopy applications. In particular, I focus on analytical and numerical analysis of pulsed stability derived for Raman lasers by using dispersion-managed telecom fibers and pumping at near 1530 nm telecom wavelengths. I show the evolution of the first and second order Stokes signals at the output for different peak pump power and the net anomalous dispersion combinations. I determine the stability condition for dispersion-managed synchronous Raman lasers up to second order. In the second part of the thesis, the noise performance of the amplified time stretched systems is investigated. Amplified time stretched systems enabling real time applications such as high-speed analog-to-digital converters, RF arbitrary waveform generation and dispersive imaging are performance limited by the noise cumulated in the system. In particular, I analyze the noise performance and hence the effective number of bits (ENOB) performance of time stretch ADCs with distributed and lumped amplifications. I estimate that distributed amplification in time stretch system with >10GHz analog bandwidth exhibit up to 16dB higher SNR corresponding to ˜2.5 bit higher resolution. The last part of the thesis introduces a novel technique of using MEMS based digital micro mirror technology as a digital spatial light modulator for fast programmable all-optical RF arbitrary waveform generation. In particular, the detailed procedure is described and the analytical modeling that discusses the limits of the proposed technique in terms achievable temporal resolution, repetition rate, modulation index and the rise/fall times of the final waveform is calculated as figure of merit. Experimental generation of square and sawtooth waveforms is demonstrated as a proof-of concept. By using the state of the art MEMS technology arbitrary waveforms up to 1GHz rate and reconfigurable in ˜30micros are achievable.

  19. Air cushion effect in the short-pulse initiation of explosives

    SciTech Connect

    Fritz, J.N.; Kennedy, J.E.

    1997-08-01

    When thin flyer plates are used to shock initiate high explosive (HE), any air present ahead of the flyer may cause a significant desensitization of the HE. The effect of the air in cushioning the impact of plastic flyers faced with metal films is analyzed here with MACRAME, a code which calculates wave interactions and traces wave propagation. The authors find that the second air shock into the HE has sufficient pressure to collapse the HE to crystal density or higher. Precompressed regions of HE do not react rapidly when the main impact pulse does arrive. Define y{sup *} as the depth where the major shock overtakes the precompression wave (for no air y{sup *} {r_arrow} 0). For various flyers and air combinations, the authors compare pressure profiles at y = y{sup *} + {epsilon}. The shock pressure profile associated with metal film impact may be greatly attenuated at the depth y{sup *}. Density profiles (p(t) at y) show that the shock heating for y > y{sup *} is greater than that for y < y{sup *}.

  20. Relativistic electron transport in wire and foil targets driven by intense short pulse lasers

    NASA Astrophysics Data System (ADS)

    Mason, R. J.; Stephens, R. B.; Wei, M.; Freeman, R. R.; Hill, J.; van Woerkom, L. D.

    2006-10-01

    We model intense laser driven electron transport in wires and foils with the new implicit hybrid code e-PLAS. We focus on background plasma heating for Fast Ignitor applications. The model tracks collisional relativistic PIC electrons undergoing scatter and drag in a background plasma of colliding cold electron and ion Eulerian fluids. Application to 10 μm diameter, 250 μm long, fully ionized carbon wires with an attached cone [Kodama et al. Nature 432 1005 (2004)], exposed to 1 ps, 10^19 W/cm^2 pulses in a 30 μm centered spot, directly calculates resistive Joule heating of the background electrons in the wire to 1.7 KeV. 150 MG magnetic fields arise at the wire surfaces corresponding to hot electron flow outside the wire and a return electron flow just within it. Shorter wires (25 μm) exhibit hot electron recycling. Preliminary simulations indicate that reduction of the cone to a 30 μm diameter nail head produces little change in these results. We also report on tapered wires, wires attached to foils, and the modifying effects of pre-plasma on electron transport into the foils.

  1. Theory of multiphoton ionization of atoms by strong, short pulsed lasers

    SciTech Connect

    Kulander, K.C.

    1987-07-10

    A numerical technique for investigating the behavior of many electron atoms in intense laser fields is presented. A description of the method is followed by results of an illustrative, application to helium for a number of wavelengths and intensities. A discussion of high order ionization dynamics for this system based on these calculations is provided. 10 refs.

  2. Computational modeling of stress transient and bubble evolution in short-pulse laser irradiated melanosome particles

    SciTech Connect

    Strauss, M.; Amendt, P.A.; London, R.A.; Maitland, D.J.; Glinsky, M.E.; Lin, C.P.; Kelly, M.W.

    1997-03-04

    Objective is to study retinal injury by subnanosecond laser pulses absorbed in the retinal pigment epithelium (RPE) cells. The absorption centers in the RPE cell are melanosomes of order 1 {mu}m radius. Each melanosome includes many melanin particles of 10-15 nm radius, which are the local absorbers of the laser light and generate a discrete structure of hot spots. This work use the hydrodynamic code LATIS (LAser-TISsue interaction modeling) and a water equation of state to first simulate the small melanin particle of 15 nm responsible for initiating the hot spot and the pressure field. A average melanosome of 1 {mu}m scale is next simulated. Supersonic shocks and fast vapor bubbles are generated in both cases: the melanin scale and the melanosome scale. The hot spot induces a shock wave pressure than with a uniform deposition of laser energy. It is found that an absorption coefficient of 6000 -8000 cm{sup -1} can explain the enhanced shock wave emitted by the melanosome. An experimental and theoretical effort should be considered to identify the mechanism for generating shock wave enhancement.

  3. Short pulse duration shock initiation experiments plus ignition and growth modeling on Composition B

    NASA Astrophysics Data System (ADS)

    May, Chadd M.; Tarver, Craig M.

    2014-05-01

    Composition B (63% RDX, 36% TNT, 1% wax) is still a widely used energetic material whose shock initiation characteristics are necessary to understand. It is now possible to shock initiate Composition B and other secondary explosives at diameters well below their characteristic failure diameters for unconfined self-sustaining detonation. This is done using very high velocity, very thin, small diameter flyer plates accelerated by electric or laser power sources. Recently experimental detonation versus failure to detonate threshold flyer velocity curves for Composition B using several KaptonTM flyer thicknesses and diameters were measured. Flyer plates with diameters of 2 mm successfully detonated Composition B, which has a nominal failure diameter of 4.3 mm. The shock pressures required for these initiations are greater than the Chapman-Jouguet (C-J) pressure in self-sustaining Composition B detonation waves. The initiation process is two-dimensional, because both rear and side rarefactions can affect the shocked Composition B reaction rates. The Ignition and Growth reactive flow model for Composition B is extended to yield accurate simulations of this new threshold velocity data for various flyer thicknesses.

  4. Interaction of a finite train of short pulses with an atomic ladder system

    SciTech Connect

    Jang, H. U.; Lomsadze, B.; Trachy, M. L.; Veshapidze, G.; Fehrenbach, C. W.; DePaola, B. D.

    2010-10-15

    When a train of optical pulses interacts with a medium, the time between pulses and the pulse-to-pulse phase jump have a profound effect on the outcome of the interaction. For a near-infinite train of regularly separated pulses having a constant pulse-to-pulse phase jump, as in the output of a frequency comb laser interacting with a ladder system, excitation of that system has been previously calculated and compared with experiment. In that case, the number of pulses in the train is very large, and the energy per pulse is very small. In the present work, the other extreme is experimentally examined: A small number of regularly spaced optical pulses are made to interact with a three-level ladder system in atomic rubidium. The pulses have been amplified, possibly placing the interactions into a nonperturbative regime. The experimental results are compared to a simple intuitive model and found to be in good general agreement. However, some aspects of the experimental results seem to be at odds with the simple model.

  5. Short pulsed gain-switched fiber laser with improved efficiency utilizing unabsorbed pump recovery.

    PubMed

    Petelin, Jaka; Agrež, Vid; Podobnik, Boštjan; Petkovšek, Rok

    2014-08-25

    A simple solution for increasing the slope efficiency of a gain-switched fiber laser based on Yb-doped active fiber is presented. By adding a fiber amplifier stage, which recovers the unabsorbed pump light from the gain-switched oscillator, a significant increase in slope efficiency is achieved. The pulses at 1030-nm wavelength have an FWHM of 28 ns and a peak power of 2.3 kW.

  6. High Energy K(alpha) Radiography Using High-intensity, Short-pulse Lasers

    SciTech Connect

    Park, H; Izumi, N; Key, M H; King, J A; Koch, J A; Landen, O L; Patel, P K; Price, D F; Remington, B A; Robey, H F; Snavely, R A; Tabak, M; Town, R J; Wickersham, J E; Stoeckl, C; Storm, M; Theobald, W; Chambers, D M; Eagelton, R; Goldsack, T; Clarke, R J; Heathcote, R; Giraldez, E; Nikroo, A; Steinman, D A; Stephens, R B; Zhang, B B

    2005-11-16

    We have performed experiments using Callisto, the Vulcan 100 TW and the Vulcan Petawatt high intensity lasers to understand the characteristics of high energy, K{alpha} x-ray sources and to implement workable radiography solutions at 20-100 keV. Our measurements show that the K{alpha} size from a simple foil target is larger than 60 {micro}m, far larger than the experiment resolution requirement. The total K{alpha} yield is independent of target thicknesses verifying that refluxing plays a major role in photon generation. Smaller radiating volumes emit brighter K{alpha} radiation. 1-D radiography experiments using small-edge-on foils resolved 10 {micro}m features with high contrast. We tested a variety of small volume 2-D point sources such as cones, wires, and embedded wires, measuring photon yields and comparing our measurements with predictions from hybrid-PIC LSP simulations. In addition to high-energy, high-resolution backlighters, future experiments will also need imaging detectors and diagnostic tools that are workable in the 20-100 keV energy range. An initial look at some of these detector issues is also presented.

  7. 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.

  8. Generation of high-order harmonics with ultra-short pulses from filamentation.

    PubMed

    Steingrube, Daniel S; Schulz, Emilia; Binhammer, Thomas; Vockerodt, Tobias; Morgner, Uwe; Kovacev, Milutin

    2009-08-31

    7-fs-pulses with 0.3 mJ are obtained after filamentation in argon and compression by double-chirped-mirrors. These pulses are used to generate high-order harmonics in a semi-infinite gas cell in different noble gases. Spectral broadening of high-order harmonics in xenon and argon is observed. In neon, an extended continuous cut-off region down to 10 nm (124 eV) is observed which is to the best of our knowledge the highest cut-off energy obtained by filamented pulses. Our result suggests the feasibility of single attosecond-pulse-generation at both high photon flux and high cut-off energy.

  9. Ultrahigh-current proton beams from short-pulse laser-solid interactions

    NASA Astrophysics Data System (ADS)

    Badziak, J.; Antici, P.; Fuchs, J.; Jabłowski, S.; Lancia, L.; Mancic, A.; Parys, P.; Rosiński, M.; Suchańska, R.; Szydłowski, A.; Wołowski, J.

    2008-05-01

    The results of studies of high-current proton beam generation from thin (1-3μm) solid targets irradiated by 0.35-ps laser pulse of intensity up to 2×1019 W/cm2 are reported. It is shown that the proton beams of multi-MA currents and multi-TA/cm2 current densities at the source can be produced when the laser-target interaction conditions approach the skin-layer ponderomotive acceleration requirements. The current and energy spectrum of protons remarkably depend on the target structure. In particular, using a double-layer Au/PS target (plastic covered by 0.1 - 0.2μm Au front layer) results in two-fold higher proton currents and higher proton energies than in the case of a plastic target.

  10. Short-pulse photoassociation in rubidium below the D{sub 1} line

    SciTech Connect

    Koch, Christiane P.; Kosloff, Ronnie; Masnou-Seeuws, Francoise

    2006-04-15

    Photoassociation of two ultracold rubidium atoms and the subsequent formation of stable molecules in the singlet ground and lowest triplet states is investigated theoretically. The method employs laser pulses inducing transitions via excited states correlated to the 5S+5P{sub 1/2} asymptote. Weakly bound molecules in the singlet ground or lowest triplet state can be created by a single pulse while the formation of more deeply bound molecules requires a two-color pump-dump scenario. More deeply bound molecules in the singlet ground or lowest triplet state can be produced only if efficient mechanisms for both pump and dump steps exist. While long-range 1/R{sup 3} potentials allow for efficient photoassociation, stabilization is facilitated by the resonant spin-orbit coupling of the 0{sub u}{sup +} states. Molecules in the singlet ground state bound by a few wave numbers can thus be formed. This provides a promising first step toward ground-state molecules which are ultracold in both translational and vibrational degrees of freedom.

  11. Gas breakdown driven by L band short-pulse high-power microwave

    SciTech Connect

    Yang Yiming; Yuan Chengwei; Qian Baoliang

    2012-12-15

    High power microwave (HPM) driven gas breakdown is a major factor in limiting the radiation and transmission of HPM. A method that HPM driven gas breakdown could be obtained by changing the aperture of horn antenna is studied in this paper. Changing the effective aperture of horn antenna can adjust the electric field in near field zone, leading to gas breakdown. With this method, measurements of air and SF{sub 6} breakdowns are carried out on a magnetically insulated transmission-line oscillators, which is capable of generating HPM with pulse duration of 30 ns, and frequency of 1.74 GHz. The typical breakdown waveforms of air and SF{sub 6} are presented. Besides, the breakdown field strengths of the two gases are derived at different pressures. It is found that the effects of air and SF{sub 6} breakdown on the transmission of HPM are different: air breakdown mainly shortens the pulse width of HPM while SF{sub 6} breakdown mainly reduces the peak output power of HPM. The electric field threshold of SF{sub 6} is about 2.4 times larger than that of air. These differences suggest that gas properties have a great effect on the transmission characteristic of HPM in gases.

  12. 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.

  13. Gas breakdown driven by L band short-pulse high-power microwave

    NASA Astrophysics Data System (ADS)

    Yang, Yi-Ming; Yuan, Cheng-Wei; Qian, Bao-Liang

    2012-12-01

    High power microwave (HPM) driven gas breakdown is a major factor in limiting the radiation and transmission of HPM. A method that HPM driven gas breakdown could be obtained by changing the aperture of horn antenna is studied in this paper. Changing the effective aperture of horn antenna can adjust the electric field in near field zone, leading to gas breakdown. With this method, measurements of air and SF6 breakdowns are carried out on a magnetically insulated transmission-line oscillators, which is capable of generating HPM with pulse duration of 30 ns, and frequency of 1.74 GHz. The typical breakdown waveforms of air and SF6 are presented. Besides, the breakdown field strengths of the two gases are derived at different pressures. It is found that the effects of air and SF6 breakdown on the transmission of HPM are different: air breakdown mainly shortens the pulse width of HPM while SF6 breakdown mainly reduces the peak output power of HPM. The electric field threshold of SF6 is about 2.4 times larger than that of air. These differences suggest that gas properties have a great effect on the transmission characteristic of HPM in gases.

  14. Mesoscale Laser Processing using Excimer and Short-Pulse Ti: Sapphire Lasers

    SciTech Connect

    Shirk, M D; Rubenchik, A M; Gilmer, G H; Stuart, B C; Armstrong, J P; Oberhelman, S K; Baker, S L; Nikitin, A J; Mariella, R P

    2003-07-28

    Targets to study high-energy density physics and inertial confinement fusion processes have very specific and precise tolerances that are pushing the state-of-the-art in mesoscale microsculpting technology. A significant effort is required in order to advance the capabilities to make these targets with very challenging geometries. Ultrashort pulsed (USP) Ti:Sapphire lasers and excimer lasers are proving to be very effective tools in the fabrication of the very small pieces that make up these targets. A brief description of the dimensional and structural requirements of these pieces will be presented, along with theoretical and experimental results that demonstrate to what extent these lasers are achieving the desired results, which include sub-{mu}m precision and RMS surface values well below 100 nm. This work indicates that excimer lasers are best at sculpting the polymer pieces and that the USP lasers work quite well on metal and aerogel surfaces, especially for those geometries that cannot be produced using diamond machining and where material removal amounts are too great to do with focused ion beam milling in a cost effective manner. In addition, the USP laser may be used as part of the procedure to fill target capsules with fusion fuel, a mixture of deuterium and tritium, without causing large perturbations on the surface of the target by keeping holes drilled through 125 {micro}m of beryllium below 5 {micro}m in diameter.

  15. Thermal interaction of short-pulsed laser focused beams with skin tissues

    NASA Astrophysics Data System (ADS)

    Jiao, Jian; Guo, Zhixiong

    2009-07-01

    Time-dependent thermal interaction is developed in a skin tissue cylinder subjected to the irradiation of a train of short laser pulses. The skin embedded with a small tumor is stratified as three layers: epidermis, dermis and subcutaneous fat with different optical, thermal and physiological properties. The laser beam is focused to the tumor site by an objective lens for thermal therapy. The ultrafast radiation heat transfer of the focused beam is simulated by the transient discrete ordinates method. The transient Pennes bio-heat equation is solved numerically by the finite volume method with alternating direction implicit scheme. Emphasis is placed on the characterization of the focused beam propagation and absorption and the temperature rise in the focal spot. The effects of the focal spot size and location, the laser power, and the bio-heat equation are investigated. Comparisons with collimated irradiation are conducted. The focused beam can penetrate a greater depth and produce higher temperature rise at the target area, and thus reduce the possibility of thermal damage to the surrounding healthy tissue. It is ideal for killing cancerous cells and small tumors.

  16. Development of high damage threshold optics for petawatt-class short-pulse lasers

    SciTech Connect

    Stuart, B.C.; Perry, M.D.; Boyd, R.D.

    1995-02-22

    The authors report laser-induced damage threshold measurements on pure and multilayer dielectrics and gold-coated optics at 1053 and 526 nm for pulse durations, {tau}, ranging from 140 fs to 1 ns. Damage thresholds of gold coatings are limited to 500 mJ/cm{sup 2} in the subpicosecond range for 1053-nm pulses. In dielectrics, qualitative differences in the morphology of damage and a departure from the diffusion-dominated {tau}1/2 scaling indicate that damage results from plasma formation and ablation for {tau}{le}10 ps and from conventional melting and boiling for {tau}>50 ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in quantitative agreement with both the pulsewidth and wavelength scaling of experimental results.

  17. Ultra-intense, short pulse laser-plasma interactions with applications to the fast ignitor

    SciTech Connect

    Wilks, S.C.; Kruer, W.L.; Young, P.E.; Hammer, J.; Tabak, M.

    1995-04-01

    Due to the advent of chirped pulse amplification (CPA) as an efficient means of creating ultra-high intensity laser light (I > 5{times}10{sup 17} W/cm{sup 2}) in pulses less than a few picoseconds, new ideas for achieving ignition and gain in DT targets with less than 1 megajoule of input energy are currently being pursued. Two types of powerful lasers are employed in this scheme: (1) channeling beams and (2) ignition beams. The current state of laser-plasma interactions relating to this fusion scheme will be discussed. In particular, plasma physics issues in the ultra-intense regime are crucial to the success of this scheme. We compare simulation and experimental results in this highly nonlinear regime.

  18. Laser-fired contact formation on metallized and passivated silicon wafers under short pulse durations

    NASA Astrophysics Data System (ADS)

    Raghavan, Ashwin S.

    The objective of this work is to develop a comprehensive understanding of the physical processes governing laser-fired contact (LFC) formation under microsecond pulse durations. Primary emphasis is placed on understanding how processing parameters influence contact morphology, passivation layer quality, alloying of Al and Si, and contact resistance. In addition, the research seeks to develop a quantitative method to accurately predict the contact geometry, thermal cycles, heat and mass transfer phenomena, and the influence of contact pitch distance on substrate temperatures in order to improve the physical understanding of the underlying processes. Finally, the work seeks to predict how geometry for LFCs produced with microsecond pulses will influence fabrication and performance factors, such as the rear side contacting scheme, rear surface series resistance and effective rear surface recombination rates. The characterization of LFC cross-sections reveals that the use of microsecond pulse durations results in the formation of three-dimensional hemispherical or half-ellipsoidal contact geometries. The LFC is heavily alloyed with Al and Si and is composed of a two-phase Al-Si microstructure that grows from the Si wafer during resolidification. As a result of forming a large three-dimensional contact geometry, the total contact resistance is governed by the interfacial contact area between the LFC and the wafer rather than the planar contact area at the original Al-Si interface within an opening in the passivation layer. By forming three-dimensional LFCs, the total contact resistance is significantly reduced in comparison to that predicted for planar contacts. In addition, despite the high energy densities associated with microsecond pulse durations, the passivation layer is well preserved outside of the immediate contact region. Therefore, the use of microsecond pulse durations can be used to improve device performance by leading to lower total contact resistances while preserving the passivation layer. A mathematical model was developed to accurately predict LFC geometry over a wide range of processing parameters by accounting for transient changes in Al and Si alloy composition within the LFC. Since LFC geometry plays a critical role in device performance, an accurate method to predict contact geometry is an important tool that can facilitate further process development. Dimensionless analysis was also conducted to evaluate the relative importance of heat and mass transfer mechanisms. It is shown that convection plays a dominant role in the heat and mass transfer within the molten pool. Due to convective mass transfer, the contacts are heavily doped with Al and Si within 10 is after contact formation, which contributes to the entire resolidified region behaving as the electrically active LFC. The validated model is also used to determine safe operating regimes during laser processing to avoid excessively high operating temperatures. By maintaining processing temperatures below a critical temperature threshold, the onset of liquid metal expulsion and loss of alloying elements can be avoided. The process maps provide a framework that can be used to tailor LFC geometry for device fabrication. Finally, using various geometric relationships for the rear side contacting scheme for photovoltaic devices, it is shown that by employing hemispherical contacts, the number of LFCs required on the rear side can be reduced 75% while doubling the pitch distance and increasing the passivation fraction. Reducing the number of backside contacts required can have a noteworthy impact of manufacturing throughput. In addition, the analytical models suggest that device performance can be maintained at levels comparable to those achieved for planar contacts when producing three-dimensional contacts. The materials and electrical characterization results, device simulations, and design considerations presented in this thesis indicate that by forming three-dimensional LFCs, performance levels of Si-based photovoltaic devices can be maintained while greatly enhancing manufacturing efficiency. The research lays a solid foundation for future development of the LFC process with microsecond pulse durations and indicates that device fabrication employing this method is a critical step moving forward.

  19. Ion acceleration in the interaction of short pulse laser radiation with the cluster-gas target

    SciTech Connect

    Fukuda, Y.; Tampo, M.; Nakamura, T.; Kando, M.; Hayashi, Y.; Yogo, A.; Sakaki, H.; Kameshima, T.; Pirozhkov, A. S.; Ogura, K.; Mori, M.; Esirkepov, T. Zh.; Bolton, P. R.; Daido, H.; Faenov, A. Ya.; Pikuz, T. A.; Boldarev, A. S.; Gasilov, V. A.; Magunov, A. I.; Kodama, R.

    2009-07-25

    We demonstrate generation of 10-20 MeV/u ions with a compact 4 TW laser using a gas target mixed with submicron clusters, corresponding to tenfold increase in the ion energies compared to previous experiments with solid targets. It is inferred that the high energy ions are generated due to formation of a strong dipole vortex structure. The demonstrated method has a potential to construct compact and high repetition rate ion sources for hadron therapy and other applications.

  20. Compression of ultra-short pulses due to cascaded second order nonlinearities in photonic bandgap structures

    NASA Astrophysics Data System (ADS)

    Joseph, Shereena; Shahid Khan, Mohd.; Hafiz, Aurangzeb Khurram

    2016-03-01

    The cascaded second order nonlinearities in a 1-D photonic bandgap structure (1-D PBG) in the spectral domain have been explored. A weak signal pulse operating at frequency of interest is seeded with a strong pulse operating at its second harmonic (SH) frequency. The interaction of both pulses in the periodic structure takes place with a particular phase mismatch condition. The intensity of SH pulse controls the propagation of signal pulse and the signal pulse exhibits pulse compression at particular input SH intensity. Considering the parameter for GaInP/InAlP PBG structure we have demonstrated pulse compression from 290 fs to 155 fs. The dependency of pulse compression on the structural parameters, group velocity mismatch, group velocity dispersion and input intensity of pump has also been explored.

  1. A phase I trial of chlorambucil administered in short pulses in patients with advanced malignancies.

    PubMed

    Blumenreich, M S; Woodcock, T M; Sherrill, E J; Richman, S P; Gentile, P S; Epremian, B E; Kubota, T T; Allegra, J C

    1988-01-01

    We carried out a phase I trial with chlorambucil. Thirty patients with advanced cancer were entered in six dose levels: 36, 48, 60, 84, 108, and 144 mg/m2. The drug was given in six divided oral doses every 6 hours and the regimen was repeated every 3 weeks. The median age was 62 years (31-84), median Karnofsky performance status (KPS) 60 (40-90). All patients but one had received prior radiation therapy, chemotherapy, or both. Central nervous system toxicity was dose limiting, occurring in 5 of 6 patients at 144 mg/m2. It was characterized by transient seizures, hallucinations, lethargy, stupor, and coma. Metoclopramide was successful in controlling nausea and vomiting, which was severe if the antiemetic was not used. Leukopenia (3 patients) and thrombocytopenia (2 patients) were mild. One patient with colorectal carcinoma had a minor response, and two patients with non-small cell lung cancer had stable disease. A safe dose for phase II trials is 108 mg/m2 in six 6-hourly oral doses.

  2. Integrated modelling framework for short pulse high energy density physics experiments

    NASA Astrophysics Data System (ADS)

    Sircombe, N. J.; Hughes, S. J.; Ramsay, M. G.

    2016-03-01

    Modelling experimental campaigns on the Orion laser at AWE, and developing a viable point-design for fast ignition (FI), calls for a multi-scale approach; a complete description of the problem would require an extensive range of physics which cannot realistically be included in a single code. For modelling the laser-plasma interaction (LPI) we need a fine mesh which can capture the dispersion of electromagnetic waves, and a kinetic model for each plasma species. In the dense material of the bulk target, away from the LPI region, collisional physics dominates. The transport of hot particles generated by the action of the laser is dependent on their slowing and stopping in the dense material and their need to draw a return current. These effects will heat the target, which in turn influences transport. On longer timescales, the hydrodynamic response of the target will begin to play a role as the pressure generated from isochoric heating begins to take effect. Recent effort at AWE [1] has focussed on the development of an integrated code suite based on: the particle in cell code EPOCH, to model LPI; the Monte-Carlo electron transport code THOR, to model the onward transport of hot electrons; and the radiation hydrodynamics code CORVUS, to model the hydrodynamic response of the target. We outline the methodology adopted, elucidate on the advantages of a robustly integrated code suite compared to a single code approach, demonstrate the integrated code suite's application to modelling the heating of buried layers on Orion, and assess the potential of such experiments for the validation of modelling capability in advance of more ambitious HEDP experiments, as a step towards a predictive modelling capability for FI.

  3. 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.

  4. Generation of heavy ion beams using high-intensity short pulse lasers

    NASA Astrophysics Data System (ADS)

    Petrov, George; McGuffey, Chris; Thomas, Alec; Krushelnick, Karl; Beg, Farhat

    2016-10-01

    A theoretical study of ion acceleration from high-Z material irradiated by intense sub-picosecond lasers is presented. The underlying physics of beam formation and acceleration is similar for light and heavy ions, however, nuances of the acceleration process make the heavy ions more challenging. At least four technical hurdles have been identified: low charge-to-mass ratio, limited number of ions amenable to acceleration, delayed acceleration and poor energy coupling due to high reflectivity of the plasma. Using two dimensional particle-in-cell (PIC) simulations, we observed transitions from Radiation Pressure Acceleration (RPA) to the Breakout Afterburner regime (BoA) and to Target Normal Sheath Acceleration (TNSA) akin to light ions. The numerical simulations predict gold ions beams with high directionality (<10 degrees half-angle), high fluxes (>1011 ions/sr) and energy (>10 MeV/nucleon) from laser systems delivering >20 J of energy on target.

  5. Free Electron Laser Short Pulse Simulation and Two-Mode Sideband Analysis

    DTIC Science & Technology

    1991-06-01

    8217_ \\ ELECTRON PATI- , Za o/ E..ECTRON’, % CASSICA - ELECRON " TRAVELLING AT 8,c V, C ~ELECTRON / RADIA m’TION SMAG NET I C Figure 2-1: Electron motion...optical wave. If electrons with an initial random dispersion in C can be made to bunch with ,/2 < < 3r 2 as they travel down the undulator, then the...dimensionless time ’r = ctIL. Note that r = 0 -- 1 as the electrons travel down the length of the undulator. The simple pendulum equation now becomes 00 C

  6. 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.

  7. Robust Short-Pulse, High-Peak-Power Laser Transmitter for Optical Communications

    NASA Technical Reports Server (NTRS)

    Wright, Malcolm W.

    2009-01-01

    We report on a pulsed fiber based master oscillator power amplifier laser at 1550 nm to support moderate data rates with high peak powers in a compact package suitable for interplanetary optical communications. To accommodate pulse position modulation, the polarization maintaining laser transmitter generates pulses from 0.1 to 1 ns with variable duty cycle over a pulse repetition frequency range of 10 to 100 MHz.

  8. 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.

  9. Atomistic modeling of nanoparticle generation in short pulse laser ablation of thin metal films in water.

    PubMed

    Shih, Cheng-Yu; Wu, Chengping; Shugaev, Maxim V; Zhigilei, Leonid V

    2017-03-01

    Laser ablation in liquids is actively used for generation of clean colloidal nanoparticles with unique shapes and functionalities. The fundamental mechanisms of the laser ablation in liquids and the key processes that control the nanoparticle structure, composition, and size distribution, however, are not yet fully understood. In this paper, we report the results of first atomistic simulations of laser ablation of metal targets in liquid environment. A model combining a coarse-grained representation of the liquid environment (parameterized for water), a fully atomistic description of laser interactions with metal targets, and acoustic impedance matching boundary conditions is developed and applied for simulation of laser ablation of a thin silver film deposited on a silica substrate. The simulations, performed at two laser fluences in the regime of phase explosion, predict a rapid deceleration of the ejected ablation plume and the formation of a dense superheated molten layer at the water-plume interface. The water in contact with the hot metal layer is brought to the supercritical state and transforms into an expanding low density metal-water mixing region that serves as a precursor for the formation of a cavitation bubble. Two distinct mechanisms of the nanoparticle formation are predicted in the simulations: (1) the nucleation and growth of small (mostly ⩽10nm) nanoparticles in the metal-water mixing region and (2) the formation of larger (tens of nm) nanoparticles through the breakup of the superheated molten metal layer triggered by the emergence of complex morphological features attributed to the Rayleigh-Taylor instability of the interface between at the superheated metal layer and the supercritical water. The first mechanism is facilitated by the rapid cooling of the growing nanoparticles in the supercritical water environment, resulting in solidification of the nanoparticles located in the upper part of the mixing region on the timescale of nanoseconds. The computational prediction of the two mechanisms of nanoparticle formation yielding nanoparticles with different characteristic sizes is consistent with experimental observations of two distinct nanoparticle populations appearing at different stages of the ablation process. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Channels of energy redistribution in short-pulse laser interactions with metal targets

    NASA Astrophysics Data System (ADS)

    Zhigilei, Leonid V.; Ivanov, Dmitriy S.

    2005-07-01

    The kinetics and channels of laser energy redistribution in a target irradiated by a short, 1 ps, laser pulse is investigated in computer simulations performed with a model that combines molecular dynamics (MD) simulations with a continuum description of the laser excitation and relaxation of the conduction band electrons, based on the two-temperature model (TTM). The energy transferred from the excited electrons to the lattice splits into several parts, namely the energy of the thermal motion of the atoms, the energy of collective atomic motions associated with the relaxation of laser-induced stresses, the energy carried away from the surface region of the target by a stress wave, the energy of quasi-static anisotropic stresses, and, at laser fluences above the melting threshold, the energy transferred to the latent heat of melting and then released upon recrystallization. The presence of the non-thermal channels of energy redistribution (stress wave and quasi-static stresses), not accounted for in the conventional TTM model, can have important implications for interpretation of experimental results on the kinetics of thermal and mechanical relaxation of a target irradiated by a short laser pulse as well as on the characteristics of laser-induced phase transformations. The fraction of the non-thermal energy in the total laser energy partitioning increases with increasing laser fluence.

  11. 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.

  12. Short-pulse excitation of microwave plasma for efficient diamond growth

    SciTech Connect

    Yamada, Hideaki Chayahara, Akiyoshi; Mokuno, Yoshiaki

    2016-08-29

    To realize a variety of potential applications of diamonds, particularly in the area of power electronics, it is indispensable to improve their growth efficiency. Most conventional approaches have tried to achieve this simply by increasing the gas temperature; however, this makes it difficult to grow large diamond crystals. To improve the growth efficiency while lowering the gas temperature, we propose that using a pulse-modulated microwave plasma with a sub-millisecond pulse width can enhance the power efficiency of the growth rate of single-crystal diamonds. We found that using a sub-millisecond pulse-mode discharge could almost double the growth rate obtained using continuous mode discharge for a fixed average microwave power and gas pressure. A comparison between experimental observations of the optical emission spectra of the discharge and a numerical simulation of the gas temperature suggests that a decrease in the gas temperature was achieved, and highlights the importance of electron-dominated reactions for obtaining the enhancement of the growth rate. This result will have a large impact in the area of diamond growth because it enables diamond growth to be more power efficient at reduced temperatures.

  13. Optoacoustic system based on 808-nm high energy short pulse diode laser stacks

    NASA Astrophysics Data System (ADS)

    Rodríguez, Sergio; Sánchez, Miguel; Leggio, Luca; Gawali, Sandeep B.; Gallego, Daniel C.; Lamela, Horacio

    2017-03-01

    In the last few decades, high power diode lasers (HPDL) have been introduced as alternative laser sources for optoacoustic imaging (OAI), due to their high repetition rates (a few kHz) for fast OA image acquisition, lower cost and size if compared to solid state lasers. Nevertheless, their drawbacks consist in a low energy per pulse (μJ) and a relatively highly divergent beam that needs collimation optics. At this purpose, the employment of diode laser stacks significantly increases the energy per pulse up to several mJ. The diode laser stacks imply a big challenge if compared to single emitters for several reasons. Firstly, they need very demanding electronic requirements, as forward voltages and currents of several tens of volts and hundreds of amperes, respectively. Secondly, their highly divergent beam profile requires precise collimation by means of fast axis and slow axis collimation. In this work, we show an 808-nm diode laser stack driven with 17 V and 200 A by a low-cost current driver for emitting pulses of 1 mJ at 1 kHz. Particular emphasis will be attributed to the design of the high current pulses driver and the optics employed to collimate and after focus the beam in a spot. The light spot will be applied to an ink inclusion hosted in turbid phantom. We demonstrate that our system is able to generate appreciable OA signals in turbid phantoms. This aspect represents a novelty in OAI systems because it is demonstrated that HPDL sources can efficiently replace solid-state lasers.

  14. Photodarkening kinetics in a high-power YDFA versus CW or short-pulse seed conditions

    NASA Astrophysics Data System (ADS)

    Jolly, Alain; Vinçont, Cyril; Boullet, Johan

    2017-02-01

    We propose an innovating model to describe the kinetics of competing photo-darkening and photo-bleaching phenomena in high-power, Ytterbium-Doped-Fibre-Amplifiers. This model makes use of aggregated species of trivalent Ytterbium and divalent ions, which operate as primarily efficient color-centers. This ensures multi-photon excitation, partly from the pump and partly from the signal. The fit of numerical computations with dedicated experiments help to validate our theoretical assumptions, in the definition of the involved physics. Potential applications of this study include further discussions for the selection of processing options with fibre-manufacturers and the optimization of operating conditions.

  15. Electron Emission from Conductors Subjected to Intense, Short-Pulse Electric Fields

    DTIC Science & Technology

    1987-06-01

    showed that for 10-ns pulse lengths, anodized alumi- num surfaces could hold off more than twice the electric field strength of bare aluminum...shorter, 3-ns pulse lengths, anodizing was less effective at improving suppression of electron emission, while surface finish became the important...pulsewidth of 10 ns. The front end of the pulser, along with a typical output pulse , is shown in Fig. 1. The vacuum coaxial line is about 6-ns long, and

  16. Measurements of emission spectra from hot, dense germanium plasma in short pulse laser experiments

    NASA Astrophysics Data System (ADS)

    Hoarty, D. J.; James, S. F.; Brown, C. R. D.; Williams, B. M.; Chung, H. K.; Harris, J. W. O.; Upcraft, L.; Crowley, B. J. B.; Smith, C. C.; Lee, R. W.

    2010-01-01

    Heating of thin foil targets by an high power laser at intensities of 10 17-10 19 W/cm 2 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 microdot made of a mixture of germanium and titanium buried at depth of 1.5 μm. The L-shell spectra from the germanium and the K-shell spectra from the titanium were taken using crystal spectrometers recording onto film and an ultra fast X-ray streak camera coupled to a conical focussing crystal with a time resolution of 1 ps. 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 were inferred from the CR modelling using FLYCHK to be 800 ± 100 eV and 1.5 ± 0.5 g/cc. The best fit to the LTE models was at a temperature 20% lower than with the CR model. Though the sample departs from LTE significantly useful spectral comparisons can still be made. The results and comparisons are discussed along with improvements to the experimental technique to achieve conditions closer to LTE.

  17. A short-pulse K(a)-band instrumentation radar for foliage attenuation measurements.

    PubMed

    Puranen, Mikko; Eskelinen, Pekka

    2008-10-01

    A portable K(a)-band instrumentation radar for foliage attenuation measurements has been designed. It uses direct dielectric resonator oscillator multiplier pulse modulation giving a half power pulse width of 17 ns. The dual conversion scalar receiver utilizes either a digital storage oscilloscope in envelope detection format or a special gated comparator arrangement providing 1 m resolution and associated led seven segment display for data analysis. The calibrated dynamic range is better than 37 dB with an equivalent noise floor of 0.005 dBsm at 25 m test range distance. First experiments indicate an effective beamwidth close to 1 degree. The total weight is below 5 kg and the unit can be mounted on a conventional photographic tripod. Power is supplied from a 12 V/6 A h sealed lead acid battery giving an operating time in excess of 10 h.

  18. Investigating the Inverse Faraday Effect with an intense short pulse laser

    NASA Astrophysics Data System (ADS)

    Najmudin, Zulfikar; Tatarakis, Michealis; Krushelnick, Karl; Clark, Eugene; Santala, Marko; Dangor, Bucker; Clarke, Robert; Neely, David; Faure, Jerome; Malka, Victor

    2000-10-01

    A circularly polarised laser beam traversing through a plasma can generate an azimuthal electron current, due to their combined quiver motion. This will generate a solenoidal magnetic field in the plasma colinear with the laser propagation. This phenomena is known as the Inverse Faraday Effect (IFE), and can result in sizeable magnetic field strength for an ultra-intense laser pulses traversing through sufficiently dense plasmas. We present here measurements of the IFE field generated by the ultra-intense Vulcan:CPA laser travelling through underdense plasmas. The Vulcan:CPA laser can be focused to greater than 5 × 10^18 Wcm-2, and can generate IFE magnetic fields in excess of 2 MG. We present here the variation of the field with intensity and density, as well as measurements of its temporal and spatial behaviour. Noticeably the field is only observed for the time duration of the driver pulse, and decreases in spatial extent with increasing strength of magnetic field.

  19. Propagation of a short-pulse laser-driven electron beam in matter

    NASA Astrophysics Data System (ADS)

    Volpe, L.; Batani, D.; Birindelli, G.; Morace, A.; Carpeggiani, P.; Xu, M. H.; Liu, F.; Zhang, Y.; Zhang, Z.; Lin, X. X.; Liu, F.; Wang, S. J.; Zhu, P. F.; Meng, L. M.; Wang, Z. H.; Li, Y. T.; Sheng, Z. M.; Wei, Z. Y.; Zhang, J.; Santos, J. J.; Spindloe, C.

    2013-03-01

    We studied the transport of an intense electron beam produced by high intensity laser pulses through metals and insulators. Targets were irradiated at two different intensities, 1017 W/cm2 and 1019 W/cm2, at the laser facility Xtreme Light XL-III in Beijing, a Ti:Sa laser source emitting 40 fs pulses at 800 nm. The main diagnostic was Cu-Kα fluorescence imaging. Images of Kα spots have been collected for those two laser intensities, for different target thickness, and for different materials. Experimental results are analyzed taking into account both collisional and collective effects as well as refluxing at the edge of the target. The target temperature is evaluated to be Tc ˜ 6 eV for intensity I = 1017 W/cm2 (for all the tested materials: plastic, aluminium, and copper), and Tc ˜ 60 eV in aluminium and 120 eV in titanium for intensity I = 1019 W/cm2.

  20. Investigation of longitudinal proton acceleration in exploded targets irradiated by intense short-pulse laser

    SciTech Connect

    Gauthier, M.; Lévy, A.; D'Humières, E.; Beaucourt, C.; Breil, J.; Feugeas, J. L.; Nicolaï, P.; Tikhonchuk, V.; Glesser, M.; Albertazzi, B.; Chen, S. N.; Dervieux, V.; Fuchs, J.; Pépin, H.; Antici, P.

    2014-01-15

    It was recently shown that a promising way to accelerate protons in the forward direction to high energies is to use under-dense or near-critical density targets instead of solids. Simulations have revealed that the acceleration process depends on the density gradients of the plasma target. Indeed, under certain conditions, the most energetic protons are predicted to be accelerated by a collisionless shock mechanism that significantly increases their energy. We report here the results of a recent experiment dedicated to the study of longitudinal ion acceleration in partially exploded foils using a high intensity (∼5 × 10{sup 18} W/cm{sup 2}) picosecond laser pulse. We show that protons accelerated using targets having moderate front and rear plasma gradients (up to ∼8 μm gradient length) exhibit similar maximum proton energy and number compared to proton beams that are produced, in similar laser conditions, from solid targets, in the well-known target normal sheath acceleration regime. Particle-In-Cell simulations, performed in the same conditions as the experiment and consistent with the measurements, allow laying a path for further improvement of this acceleration scheme.

  1. Short-Pulse Electron-Beam Propagation Experiments in a Controlled-Environment Chamber.

    DTIC Science & Technology

    1982-03-08

    pressures (400-550 Pa), magnetic probe data were used to estimate induced electric fields and nose erosion caused by ohmic energy loss . Results were...formation. For those shots where propagation was observed at pressures above 550 Pa, Faraday cuD traces show a loss of the beam tail. ’II I UNCLASSIFIED...the drift tube. At high pressures, propagation was limited by a lack of a stable pinch equilibrium, with losses predominantly at the beam tail. At the

  2. Heat accumulation effects in short-pulse multi-pass cutting of carbon fiber reinforced plastics

    NASA Astrophysics Data System (ADS)

    Kononenko, T. V.; Freitag, C.; Komlenok, M. S.; Onuseit, V.; Weber, R.; Graf, T.; Konov, V. I.

    2015-09-01

    The formation of a matrix evaporation zone (MEZ) in carbon fiber reinforced plastics during multi-pass laser cutting with picosecond laser pulses is studied for a wide range of pulse frequencies (fp = 10-800 kHz) and feed rates (vf = 0.002-10 m/s). Three regimes of the formation of the MEZ are found and related with different heat accumulation effects: (i) small MEZ (<2 μm) with negligible heat accumulation, (ii) moderate-size MEZ (up to a few hundred microns) determined by heat accumulation between pulses, and (iii) large MEZ (up to a few millimeters) caused by heat accumulation between scans. The dependence of the size of the MEZ on the number of scans and the scan frequency was studied to distinguish the two heat accumulation effects (between pulses and between scans), which occur on different time-scales. A diagram to illustrate the boundaries between the three regimes of the formation of the MEZ as a function of feed rate and pulse frequency is proposed as a promising base for further studies and as a useful tool to optimize the processing parameters in practice.

  3. Short-pulse high-current-density photoemission in high electric fields

    SciTech Connect

    Fischer, J.; Srinivasan-Rao, T.

    1987-01-01

    We present the experimental results of photoemission studies on thin wires of gold-coated tungsten, held at surface fields in the range of 10/sup 6/ to 3 x 10/sup 8/ V/m, and illuminated by 10 ps long, 4.66 eV photon laser pulses. The wire cathodes arranged coaxially in an anode experienced a surface-field enhancement of 10/sup 2/ to 10/sup 3/ over the applied voltage. We obtained current densities exceeding 10 kA/cm/sup 2/ from a 50 ..mu..m diameter wire, from a (50 x 400) ..mu..m/sup 2/ area, under partially space-change-limited conditions. The quantum efficiency for emission-limited cases was in the range of 10/sup -5/. For these cases results using 50 ..mu..m and 4 ..mu..m diameter wires indicated linear dependence of charge density with optical energy density. The emission also scaled linearly with the emitting area. For surface fields above 3 x 10/sup 7/ V/m, a twofold enhancement of emission was observed for a tenfold increase in the field. 7 refs., 9 figs.

  4. Optical damage performance measurements of multilayer dielectric gratings for high energy short pulse lasers

    NASA Astrophysics Data System (ADS)

    Alessi, D.; Carr, C. W.; Negres, R. A.; Hackel, R. P.; Stanion, K. A.; Cross, D. A.; Guss, G.; Nissen, J. D.; Luthi, R.; Fair, J. E.; Britten, J. A.; Haefner, C.

    2015-02-01

    We investigate the laser damage resistance of multilayer dielectric (MLD) diffraction gratings used in the pulse compressors for high energy, high peak power laser systems such as the Advanced Radiographic Capability (ARC) Petawatt laser on the National Ignition Facility (NIF). Our study includes measurements of damage threshold and damage density (ρ(Φ)) with picosecond laser pulses at 1053 nm under relevant operational conditions. Initial results indicate that sparse defects present on the optic surface from the manufacturing processes are responsible for damage initiation at laser fluences below the damage threshold indicated by the standard R-on-1 test methods, as is the case for laser damage with nanosecond pulse durations. As such, this study supports the development of damage density measurements for more accurate predictions on the damage performance of large area optics.

  5. 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.

  6. Control and ultra-short pulse generation in stimulated Raman backscattering

    NASA Astrophysics Data System (ADS)

    Škorić, Miloš M.; Nikolić, Ljubomir; Hadžievski, Ljupčo; Batani, Dimitri; Ishiguro, Seiji; Mima, Kunioki

    2016-03-01

    A stimulated Raman scattering (SRS) is a great concern for laser fusion, causing an energy and symmetry loss and target preheating. In particular, for dominating backward- SRS (BRS), a complexity of nonlinear saturation was revealed. Recently, to develop lasers at multi-exawatts and beyond, relevant to high-energy physics, a proposed Raman amplification based on BRS met a restrictive operation window. Here, we stress BRS generics that due to a nonlinear frequency shift (relativistic/trapping effect), it nonlinearly saturates with intermittent pulsations. A “break up” of Manley-Rowe invariants explains a non-steady saturation. Further, a coherent pulsation BRS regime is proposed for femto-sec pulse generation in a thin exploding foil plasma, with parameter scalings investigated by analytics and particle simulations.

  7. 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 pressures of 15-30 bar extensive clustering of the low percentage (0.1-0.5%) seeded molecules in He and Ne carrier gasses can be produced of interest for cluster research.

  8. Short pulse acquisition by low sampling rate with phase-coded sequence in lidar system

    NASA Astrophysics Data System (ADS)

    Wu, Long; Xu, Jiajia; Lv, Wentao; Yang, Xiaocheng

    2016-11-01

    The requirement of high range resolution results in impractical collection of every returned laser pulse due to the limited response speed of imaging detectors. This paper proposes a phase coded sequence acquisition method for signal preprocessing. The system employs an m-sequence with N bits for demonstration with the detector controlled to accumulate N+1 bits of the echo signals to deduce one single returned laser pulse. An indoor experiment achieved 2 μs resolution with the sampling period of 28 μs by employing a 15-bit m-sequence. This method shows the potential to improve the detection capabilities of narrow laser pulses with the detectors at a low frame rate, especially for the imaging lidar systems. Meanwhile, the lidar system is able to improve the range resolution with available detectors of restricted performance.

  9. e-PLAS calculation of short pulse heating in wire targets

    NASA Astrophysics Data System (ADS)

    Mason, R. J.; Beg, F. N.; Stephens, R.; van Woerkom, L.; Freeman, R. R.

    2008-11-01

    The 2-D implicit hybrid simulation code e-PLAS has been used to model energy deposition and hot electron transport in a variety of wire targets (e.g. Cu wires with nail or cone heads) [1]. Implicit E&B-fields [2] permit the use of large cells and time steps while avoiding finite grid heating. Van Leer background plasma fluids allow for ps-long simulations of ˜700 μm wires on a PC with economy. For ˜1.7x10^20 W/cm^2 pulse intensities we compare results from the use of Cartesian and cylindrical modeling geometry. We probe the effects of cold background electron-ion scatter [3], resistive E-fields and hot electron drag on the background heating. Temperature limitation from target ionization is explored. B-field trapping of hot electrons generated near critical density is examined as a function of the emission isotropy, energy spectrum, and plasma gradient scale length. Integrated simulations of the absorption and hot electron generation will be discussed. [1] J. Pasley et al., Phys. Plas. 14, 120701 (2007). [2] R. J. Mason, J. Comp. Phys. 71, 429 (1987). [3] R. J. Mason, Phys. Rev. Lett. 96, 035001 (2006).

  10. Electrophysical and optophysical properties of air ionized by a short pulse of fast electrons

    NASA Astrophysics Data System (ADS)

    Vagin, Iu. P.; Stal', N. L.; Khokhlov, V. D.; Chernoiarskii, A. A.

    A method for solving the nonstationary kinetic equation of electron deceleration is developed which is based on the multigroup approximation. The electron distribution function in air ionized by nonstationary sources of primary electrons is determined, and the avalanche formation of secondary electrons is considered. Theoretical and experimental results are presented on the time dependence of the air luminescence intensity in two spectral intervals, one including the 391.4 nm N2(+) band and the other including the 337.1 nm N2 band, for different values of gas pressure under the effect of a short beam of electrons with energies of 100 keV.

  11. 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.

  12. Calculated Thermal Response of High-Power Switch to Short Pulses

    DTIC Science & Technology

    2013-10-01

    space of 4 or 5 seconds (s). Modeling and simulation were performed with SolidWorks * 3D modeling software and SolidWorks Simulation computational... SolidWorks is a registered trademark of Dassault Systèmes SolidWorks Corporation. 2 while attempting to preserve the dimensions and volume of the

  13. 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.

  14. Heating in short-pulse laser-driven cone-capped wire targets

    NASA Astrophysics Data System (ADS)

    Mason, R. J.; Wei, M.; King, J.; Beg, F.; Stephens, R. B.

    2007-11-01

    The 2-D implicit hybrid simulation code e-PLAS has been used to study heating in cone-capped copper wire targets. The code e-PLAS tracks collisional particle-in-cell (PIC) electrons traversing background plasma of collisional Eulerian cold electron and ion fluids. It computes E- and B-fields by the Implicit Moment Method [1,2]. In recent experiments [3] at the Vulcan laser facility, sub- picosecond laser pulses at 1.06 μm, and 4.0 x 10^20 W/cm^2 intensity were focused into thin-walled (˜10 μm) cones attached to copper wires. The wire diameter was varied from 10-40 μm with a typical length of 1 mm. We characterize heating of the wires as a function of their diameters and length, and relate modifications of this heating to changes in the assumed laser-generated hot electron spectrum and directivity. As in recent nail experiments [4], the cones can serve as reservoirs for hot electrons, diverting them from passage down the wires. [1] R. J. Mason, and C. Cranfill, IEEE Trans. Plasma Sci. PS-14, 45 (1986). [2] R. J. Mason, J. Comp. Phys. 71, 429 (1987). [3] J. King et al., to be submitted to Phys. Rev. Lett.. [4] R. J. Mason, M. Wei, F. Beg, R. Stephens, and C. Snell, in Proc. of ICOPS07, Albuquerque, NM, June 17-22, 2007, Talk 7D4.

  15. Aero-elastic Parameter Estimation of a 2.5 MW Wind Turbine Through Dynamic Analysis of In-Operation Vibration Data

    NASA Astrophysics Data System (ADS)

    Ozbek, Muammer; Rixen, Daniel J.

    Aero-elastic parameters of a 2.5 MW—80 m diameter—wind turbine were extracted by using the in-operation vibration data recorded for various wind speeds and operating conditions. The data acquired by 8 strain gauges (2 sensors on each blade and 2 sensors on the tower) installed on the turbine was analyzed by using OMA (Operational Modal Analysis) methods while several turbine parameters (eigenfrequencies and damping ratios) were extracted. The obtained system parameters were then qualitatively compared with the results presented in a study from literature, which includes both aeroelastic simulations and in-field measurements performed on a similar size and capacity wind turbine.

  16. High-energy proton generation from thin-foil targets with a high-intensity ultra-short pulse laser

    SciTech Connect

    Sagisaka, Akito; Daido, Hiroyuki; Yogo, Akifumi; Ogura, Koichi; Orimo, Satoshi; Ma, Jinglong; Mori, Michiaki; Nishiuchi, Mamiko; Pirozhkov, Alexander S.; Bulanov, Sergei V.; Esirkepov, Timur Zh.; Oishi, Yuji; Nayuki, Takuya; Fujii, Takashi; Nemoto, Koshichi

    2008-06-24

    We observe the proton signals with thin-foil polyimide and copper targets with a high-intensity Ti:sapphire laser pulse. High-energy protons with the maximum energy of 2.3 MeV for 7.5 {mu}m thick polyimide target and 1.2 MeV for 3 {mu}m thick copper target are generated at the laser intensity of {approx}1x10{sup 19} W/cm{sup 2} under preformed plasma condition.

  17. 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.

  18. Note: A short-pulse high-intensity molecular beam valve based on a piezoelectric stack actuator

    SciTech Connect

    Abeysekera, Chamara; Joalland, Baptiste; Shi, Yuanyuan; Kamasah, Alexander; Oldham, James M.; Suits, Arthur G.

    2014-11-15

    Solenoid and piezoelectric disk valves, which are widely used to generate molecular beam pulses, still suffer from significant restrictions, such as pulse durations typically >50 μs, low repetition rates, and limited gas flows and operational times. Much of this arises owing to the limited forces these actuators can achieve. To overcome these limitations, we have developed a new pulsed valve based on a high-force piezoelectric stack actuator. We show here that operation with pulse durations as low as 20 μs and repetition rates up to 100 Hz can be easily achieved by operating the valve in conjunction with a commercial fast high-voltage switch. We outline our design and demonstrate its performance with molecular beam characterization via velocity map ion imaging.

  19. Spatially and Temporally Resolved Atomic Oxygen Measurements in Short Pulse Discharges by Two Photon Laser Induced Fluorescence

    NASA Astrophysics Data System (ADS)

    Lempert, Walter; Uddi, Mruthunjaya; Mintusov, Eugene; Jiang, Naibo; Adamovich, Igor

    2007-10-01

    Two Photon Laser Induced Fluorescence (TALIF) is used to measure time-dependent absolute oxygen atom concentrations in O2/He, O2/N2, and CH4/air plasmas produced with a 20 nanosecond duration, 20 kV pulsed discharge at 10 Hz repetition rate. Xenon calibrated spectra show that a single discharge pulse creates initial oxygen dissociation fraction of ˜0.0005 for air like mixtures at 40-60 torr total pressure. Peak O atom concentration is a factor of approximately two lower in fuel lean (φ=0.5) methane/air mixtures. In helium buffer, the initially formed atomic oxygen decays monotonically, with decay time consistent with formation of ozone. In all nitrogen containing mixtures, atomic oxygen concentrations are found to initially increase, for time scales on the order of 10-100 microseconds, due presumably to additional O2 dissociation caused by collisions with electronically excited nitrogen. Further evidence of the role of metastable N2 is demonstrated from time-dependent N2 2^nd Positive and NO Gamma band emission spectroscopy. Comparisons with modeling predictions show qualitative, but not quantitative, agreement with the experimental data.

  20. Unmasking the functions of the chromaffin cell α7 nicotinic receptor by using short pulses of acetylcholine and selective blockers

    PubMed Central

    López, Manuela G.; Montiel, Carmen; Herrero, Carlos J.; García-Palomero, Esther; Mayorgas, Inés; Hernández-Guijo, Jesús M.; Villarroya, M.; Olivares, Román; Gandía, Luis; McIntosh, J. Michael; Olivera, Baldomero M.; García, Antonio G.

    1998-01-01

    Methyllycaconitine (MLA), α-conotoxin ImI, and α-bungarotoxin inhibited the release of catecholamines triggered by brief pulses of acetylcholine (ACh) (100 μM, 5 s) applied to fast-superfused bovine adrenal chromaffin cells, with IC50s of 100 nM for MLA and 300 nM for α-conotoxin ImI and α-bungarotoxin. MLA (100 nM), α-conotoxin ImI (1 μM), and α-bungarotoxin (1 μM) halved the entry of 45Ca2+ stimulated by 5-s pulses of 300 μM ACh applied to incubated cells. These supramaximal concentrations of α7 nicotinic receptor blockers depressed by 30% (MLA), 25% (α-bungarotoxin), and 50% (α-conotoxin ImI) the inward current generated by 1-s pulses of 100 μM ACh, applied to voltage-clamped chromaffin cells. In Xenopus oocytes expressing rat brain α7 neuronal nicotinic receptor for acetylcholine nAChR, the current generated by 1-s pulses of ACh was blocked by MLA, α-conotoxin ImI, and α-bungarotoxin with IC50s of 0.1 nM, 100 nM, and 1.6 nM, respectively; the current through α3β4 nAChR was unaffected by α-conotoxin ImI and α-bungarotoxin, and weakly blocked by MLA (IC50 = 1 μM). The functions of controlling the electrical activity, the entry of Ca2+, and the ensuing exocytotic response of chromaffin cells were until now exclusively attributed to α3β4 nAChR; the present results constitute the first evidence to support a prominent role of α7 nAChR in controlling such functions, specially under the more physiological conditions used here to stimulate chromaffin cells with brief pulses of ACh. PMID:9826675