WorldWideScience

Sample records for 39k pulsed endor

  1. Superconducting MgB2 Thin Films with Tc ≈ 39 K Grown by Pulsed Laser Deposition

    王淑芳; 戴守愚; 周岳亮; 陈正豪; 崔大复; 许佳迪; 何萌; 吕惠宾; 杨国桢

    2001-01-01

    Superconducting MgB2 thin films were fabricated on Al2 O3 (0001) substrates under ex situ processing conditions.Boron thin films were deposited by pulsed laser deposition followed by a post-annealing process. Resistance measurements of the deposited MgB2 films show Tc of ~39 K, while scanning electron microscopy and x-ray vdiffraction analysis indicate that the films consist of well-crystallized grains with a highly c-axis-oriented structure.

  2. Pulsed EPR and ENDOR study of SiC nanopowders

    Savchenko, Dariia

    Warsaw : Polish Academy of Sciences, 2014, s. 1063-1065. ISSN 0587-4246. [International School and Conference on the Physics of Semiconductors /43./. Wisla (PL), 07.06.2014-12.06.2014] R&D Projects: GA ČR GP13-06697P; GA MŠk(CZ) LM2011029 Grant ostatní: SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : EPR * ENDOR * SiC nanopowders * size effect Subject RIV: BM - Solid Matter Physics ; Magnetism

  3. Superhyperfine interactions of the nitrogen donors in 4H SiC studied by pulsed ENDOR and TRIPLE ENDOR spectroscopy

    Savchenko, Dariia; Kalabukhova, E.N.; Mokhov, E.N.; Pöppl, A.

    Zurich : Trans Tech Publications Ltd, 2013 - (Lebedev, A.; Davydov, S.; Ivanov, P.; Levinshtein, M.), s. 439-442 ISSN 0255-5476. - (Materials Science Forum. 740-742). [European Conference on Silicon Carbide and Related Materials /9./. St. Petersburg (RU), 02.09.2012-06.09.2012] R&D Projects: GA MŠk(CZ) LM2011029 Grant ostatní: SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : nitrogen donors * 4H SiC * ENDOR Subject RIV: BM - Solid Matter Physics ; Magnetism http://www.scientific.net/MSF.740-742.439

  4. Electronic structure of the nitrogen donors in 6H SiC as studied by pulsed ENDOR and TRIPLE ENDOR spectroscopy

    Savchenko, Dariia; Kalabukhova, E.N.; Pöppl, A.; Shanina, B.D.

    2012-01-01

    Roč. 249, č. 11 (2012), s. 2167-2178. ISSN 0370-1972 R&D Projects: GA MŠk(CZ) LM2011029 Grant ostatní: The Center for Analysis of Functional Materials(CZ) CZ.2.16/3.1.00/22132 Institutional research plan: CEZ:AV0Z10100522 Keywords : 6H SiC * electron ic structure * ENDOR * nitrogen donors Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.489, year: 2012

  5. Feshbach resonances in ultracold {sup 39}K

    D' Errico, Chiara [LENS and Dipartimento di Fisica, Universita di Firenze, Via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Zaccanti, Matteo [LENS and Dipartimento di Fisica, Universita di Firenze, Via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Fattori, Marco [Museo Storico della Fisica e Centro Studi e Ricerche ' Enrico Fermi' , Compendio del Viminale, 00184 Roma (Italy); Roati, Giacomo [LENS and Dipartimento di Fisica, Universita di Firenze, Via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Inguscio, Massimo [LENS and Dipartimento di Fisica, Universita di Firenze, Via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Modugno, Giovanni [LENS and Dipartimento di Fisica, Universita di Firenze, Via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Simoni, Andrea [Laboratoire de Physique des Atomes, Lasers, Molecules et Surfaces, UMR 6627 du CNRS and Universite de Rennes, 35042 Rennes Cedex (France)

    2007-07-15

    We discover several magnetic Feshbach resonances in collisions of ultracold {sup 39}K atoms, by studying atom losses and molecule formation. Accurate determination of the magnetic-field resonance locations allows us to optimize a quantum collision model for potassium isotopes. We employ the model to predict the magnetic-field dependence of scattering lengths and of near-threshold molecular levels. Our findings will be useful to plan future experiments on ultracold {sup 39}K atoms and molecules.

  6. EPR, ESE, and pulsed ENDOR study of the nitrogen donors in 15R SiC grown under carbon-rich conditions

    Savchenko, Dariia; Kalabukhova, E.; Shanina, B.; Pöppl, A.; Yukhymchuk, V.; Lančok, Ján; Ubyivovk, E.; Mokhov, E.

    2014-01-01

    Roč. 252, č. 3 (2014), s. 566-572. ISSN 0370-1972 R&D Projects: GA ČR GP13-06697P; GA MŠk(CZ) LM2011029 Grant ostatní: SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : ENDOR * nitrogen donors * 15R SiC * stoichiometry Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.489, year: 2014

  7. 39K Bose-Einstein condensate with tunable interactions.

    Roati, G.; Zaccanti, M.; D'Errico, C; Catani, Jacopo; Modugno, Michele; Simoni, Andrea; Inguscio, M.; Inguscio, Massimo

    2007-01-01

    We produce a Bose-Einstein condensate of 39K atoms. Condensation of this species with a naturally small and negative scattering length is achieved by a combination of sympathetic cooling with 87Rb and direct evaporation, exploiting the magnetic tuning of both inter- and intraspecies interactions at Feshbach resonances. We explore the tunability of the self-interactions by studying the expansion and the stability of the condensate. We find that a 39K condensate is interesting for future experi...

  8. EPR and (57)Fe ENDOR investigation of 2Fe ferredoxins from Aquifex aeolicus.

    Cutsail, George E; Doan, Peter E; Hoffman, Brian M; Meyer, Jacques; Telser, Joshua

    2012-12-01

    We have employed EPR and a set of recently developed electron nuclear double resonance (ENDOR) spectroscopies to characterize a suite of [2Fe-2S] ferredoxin clusters from Aquifex aeolicus (Aae Fd1, Fd4, and Fd5). Antiferromagnetic coupling between the Fe(II), S = 2, and Fe(III), S = 5/2, sites of the [2Fe-2S](+) cluster in these proteins creates an S = 1/2 ground state. A complete discussion of the spin-Hamiltonian contributions to g includes new symmetry arguments along with references to related FeS model compounds and their symmetry and EPR properties. Complete (57)Fe hyperfine coupling (hfc) tensors for each iron, with respective orientations relative to g, have been determined by the use of "stochastic" continuous wave and/or "random hopped" pulsed ENDOR, with the relative utility of the two approaches being emphasized. The reported hyperfine tensors include absolute signs determined by a modified pulsed ENDOR saturation and recovery (PESTRE) technique, RD-PESTRE-a post-processing protocol of the "raw data" that comprises an ENDOR spectrum. The (57)Fe hyperfine tensor components found by ENDOR are nicely consistent with those previously found by Mössbauer spectroscopy, while accurate tensor orientations are unique to the ENDOR approach. These measurements demonstrate the capabilities of the newly developed methods. The high-precision hfc tensors serve as a benchmark for this class of FeS proteins, while the variation in the (57)Fe hfc tensors as a function of symmetry in these small FeS clusters provides a reference for higher-nuclearity FeS clusters, such as those found in nitrogenase. PMID:22872138

  9. Production of strongly bound 39K bright solitons

    Lepoutre, S; Boissé, A; Berthet, G; Salomon, G; Aspect, A; Bourdel, T

    2016-01-01

    We report on the production of 39 K matter-wave bright solitons, i.e., 1D matter-waves that propagate without dispersion thanks to attractive interactions. The volume of the soliton is studied as a function of the scattering length through three-body losses, revealing peak densities as high as $\\sim 5 \\times 10^{20} m^{-3}$. Our solitons, close to the collapse threshold, are strongly bound and will find applications in fundamental physics and atom interferometry.

  10. All optical cooling of $^{39}$K to Bose Einstein condensation

    Salomon, Guillaume; Lepoutre, Steven; Aspect, Alain; Bourdel, Thomas

    2014-01-01

    We report the all-optical production of Bose Einstein condensates (BEC) of $^{39}$K atoms. We directly load $3 \\times 10^{7}$ atoms in a large volume optical dipole trap from gray molasses on the D1 transition. We then apply a small magnetic quadrupole field to polarize the sample before transferring the atoms in a tightly confining optical trap. Evaporative cooling is finally performed close to a Feshbach resonance to enhance the scattering length. Our setup allows to cross the BEC threshold with $3 \\times 10^5$ atoms every 7s. As an illustration of the interest of the tunability of the interactions we study the expansion of Bose-Einstein condensates in the 1D to 3D crossover.

  11. High Precision 40K/39K Ratio Determination

    Naumenko, M. O.; Mezger, K.; Nagler, T. F.; Villa, I. M.

    2012-12-01

    Potassium is one of the eight most abundant chemical elements in the Earth's crust and a major element in many rock-forming minerals. The isotope 40K is radioactive and undergoes β- decay to 40Ca (ca. 89.3%) and electron capture to 40Ar (ca. 10.7%). Both decays can potentially be used as dating systems. The most commonly used branch is the decay of 40K to 40Ar because it can yield highly precise ages. Both decay schemes rely on the knowledge of the 40K branching ratio and the natural 40K abundance. A 40K abundance of 0.011672±41 % was measured on terrestrial material [1]. The relative uncertainty of 0.35 % has not been improved since. Recent improvements in the precision of mass spectrometric measurements have led to the situation that the uncertainties on the K decay constant and the abundance of 40K are a major source of uncertainty on the measured ages. A more precise definition of the 40K decay constant was attempted by different research groups within the last decade [2-9] but the goal of obtaining 0.1 % relative uncertainty on K-Ar ages for geological materials, as requested by the EARTHtime initiative, has not been achieved yet. In order to improve on this situation we studied the abundances of the K isotopes in terrestrial standards. A ThermoFischer Triton+ thermal ionisation mass spectrometer was used for K isotope ratio measurements of the NIST SRM 918b K standard loaded on Ta filaments with 0.1M phosphoric acid. Three techniques were applied: (A) dynamic measurement with in-run normalisation to the IUPAC value 41K/39K=0.072168; (B) a simple total evaporation procedure; (C) the "NBL-modified" total evaporation [10]. The 40K ion beam was measured in a Faraday cup with a 1E12 Ω resistor; 39K and 41K were collected in Faraday cups with 1E11 Ω resistors. Amplifier gains were intercalibrated by supplying fixed voltages off-line. Different measurement techniques were combined with different loading procedures. We also tested ionisation yields for the

  12. Accelerated Thermalisation of 39K atoms in a Magnetic Trap with Superimposed Optical Potential

    Nath, Dipankar; Rajalakshmi, G; Unnikrishnan, C S

    2013-01-01

    We report the rapid accelerated thermalisation of Potassium 39 K atoms loaded in a magnetic trap, in the presence of a single dipole trap beam. More than an order of magnitude reduction in the thermalisation time, to less than a second, is observed with the focused off- resonant beam occupying only 0.01% of the volume of the magnetic trap. The cold atoms are loaded from a Magneto-Optical Trap(MOT) of 39 K that has gone through a compressed MOT and sub-Doppler cooling stage. The atoms are prepared in the magnetically stretched |F = 2, mF = 2> state prior to loading into the hybrid trap. We also report a direct loading of 39 K atoms, prepared in the state |F = 1>, into a single beam dipole trap.

  13. ENDOR study of CO2- radicals in hydroxyapatite of γ-irradiated bone

    ENDOR spectra and ENDOR-induced EPR spectra (dependences of ENDOR signals vs. the value of magnetic field B) of γ-irradiated bone plates and powders are studied. Typical ENDOR spectrum consisted of two signals centred at the Larmor frequencies of 1H and 31P nuclei, respectively. The ENDOR signals were found to be the superposition of the signals of axial (oriented) and orthorhombic (disordered) CO2- radicals. Changes of the ratio between the ENDOR signal intensities for g|| and gperpendicular at the rotation of the plate in the magnetic field is explained by the orientation-dependent redistribution of the EPR spectral density. EI-EPR spectra satisfactorily coincide with the spectra of conventional EPR absorption. Changes of ENDOR spectrum at the annealing of a sample before γ-irradiation (Tann = 400 oC) are explained by Larmor ENDOR mechanism. Larmor ENDOR mechanism is associated with diffusive polarization of distant (far from a paramagnetic center) 'free' nuclei under the conditions of EPR signal saturation and their depolarization by radio-frequency field in ENDOR.

  14. Quantum interference-enhanced deep sub-Doppler cooling of 39 K atoms beyond gray molasses

    Nath, Dipankar; Rajalakshmi, G; Unnikrishnan, C S

    2013-01-01

    We report enhanced sub-Doppler cooling of the bosonic atoms of 39 K facilitated by formation of dark states due to the quantum interference of excitation amplitudes in the Raman configuration for the cooling and repumping lasers tuned around the D1 resonance. The temperature of about 12 {\\mu}K achieved in the two stage D2-D1 molasses is the lowest ever reported for 39 K and spans a very large parameter region where quantum interference persists robustly. We also present results on enhanced radiation heating with sub-natural linewidth (0.1{\\Gamma}) and Fano like profile, following the quantum features of 3-level coherently driven atomic system with complexities associated with optical pumping to dark states and Sisyphus effect in standing wave light fields, over and above the Raman quantum interference.

  15. 13C- and 1H-ENDOR studies of a phenoxyl type radical

    13C- and 1H-ENDOR studies on a phenoxyl type radical in fluid solution are reported. The 13C-ENDOR resonance lines are comparable with those of the protons concerning amplitude, linewidth, and optimum experimental conditions. These findings are in contrast to previous ENDOR experiments on other 13C-labelled systems and can be explained by assuming similar hfs anisotropies for carbon-13 and protons in this radical. From saturation measurements the relaxation parameters were determined. The hyperfines couplings are discussed in terms of McLachlan and INDO calculations. For the first time natural abundance 13C-ENDOR measurement have been successful. (orig.) 891 WBU

  16. In vivo observation of quadrupolar splitting in (39)K magnetic resonance spectroscopy of human muscle tissue.

    Rösler, M B; Nagel, A M; Umathum, R; Bachert, P; Benkhedah, N

    2016-04-01

    The purpose of this work was to explore the origin of oscillations of the T(*)2 decay curve of (39)K observed in studies of (39)K magnetic resonance imaging of the human thigh. In addition to their magnetic dipole moment, spin-3/2 nuclei possess an electric quadrupole moment. Its interaction with non-vanishing electrical field gradients leads to oscillations in the free induction decay and to splitting of the resonance. All measurements were performed on a 7T whole-body MRI scanner (MAGNETOM 7T, Siemens AG, Erlangen, Germany) with customer-built coils. According to the theory of quadrupolar splitting, a model with three Lorentzian-shaped peaks is appropriate for (39)K NMR spectra of the thigh and calf. The frequency shifts of the satellites depend on the angle between the calf and the static magnetic field. When the leg is oriented parallel to the static magnetic field, the satellites are shifted by about 200 Hz. In the thigh, rank-2 double quantum coherences arising from anisotropic quadrupolar interaction are observed by double-quantum filtration with magic-angle excitation. In addition to the spectra, an image of the thigh with a nominal resolution of (16 × 16 × 32) mm(3) was acquired with this filtering technique in 1:17 h. From the line width of the resonances, (39)K transverse relaxation time constants T(*)2, fast  = (0.51 ± 0.01) ms and T(*)2, slow  = (6.21 ± 0.05) ms for the head were determined. In the thigh, the left and right satellite, both corresponding to the short component of the transverse relaxation time constant, take the following values: T(*)2, fast  = (1.56 ± 0.03) ms and T(*)2, fast  = (1.42 ± 0.03) ms. The centre line, which corresponds to the slow component, is T(*)2, slow  = (9.67 ± 0.04) ms. The acquisition time of the spectra was approximately 10 min. Our results agree well with a non-vanishing electrical field gradient interacting with (39)K nuclei in the intracellular space of

  17. Gray molasses cooling of $^{39}$K to a high phase-space density

    Salomon, Guillaume; Fouché, Lauriane; Wang, Pengjun; Aspect, Alain; Bouyer, Philippe; Bourdel, Thomas

    2013-01-01

    We present new techniques in cooling $^{39}$K atoms using laser light close to the D1 transition. First, a new compressed-MOT configuration is taking advantage of gray molasses type cooling induced by blue-detuned D1 light. It yields an optimized density of atoms. Then, we use pure D1 gray molasses to further cool the atoms to an ultra-low temperature of 6\\,$\\mu$K. The resulting phase-space density is $2\\times 10^{-4}$ and will ease future experiments with ultracold potassium. As an example, ...

  18. ENDOR of odd Gd+3 isotopes in yttrium orthovanadate

    Results of studying the intrinsic superfine (ISI) and quadrupole (QI) interaction of odd gadolinium isotopes in a YVO4 crystal by nutation ENDOR method are described. It is assumed that the main reason for a notable difference of 155GdVO4 and 155Gd3+ quadrupole interaction parameters in YVO4 consists in the exchange and dipole-dipole interaction in GdVO4, with P20 increase in yttrium orthovanadate as compared to GdVO4 being accompanied by a reduction of b20 according to the absolute value. 8 refs., 2 tabs

  19. Quantum-interference-enhanced deep sub-Doppler cooling of 39K atoms in gray molasses

    Nath, Dipankar; Easwaran, R. Kollengode; Rajalakshmi, G.; Unnikrishnan, C. S.

    2013-11-01

    We report enhanced sub-Doppler cooling of the bosonic atoms of 39K facilitated by formation of dark states with the cooling and repumping lasers tuned to the Raman resonance in Λ configuration near the D1 transition. A temperature of about 12 μK and phase-space density >2×10-5 is achieved in the two-stage D2-D1 molasses and spans a very large parameter region where quantum interference persists robustly. We also present results on enhanced radiation heating with a subnatural linewidth (0.07Γ) and a signature Fano-like profile of a coherently driven three-level atomic system. The optical Bloch equations relevant for the three-level atom in a bichromatic light field are solved with the method of continued fractions to show that cooling occurs only for a small velocity class of atoms, emphasizing the need for precooling in the D2 molasses stage.

  20. Gray-molasses cooling of 39K to a high phase-space density

    Salomon, G.; Fouché, L.; Wang, P.; Aspect, A.; Bouyer, P.; Bourdel, T.

    2013-12-01

    We present new techniques in cooling 39K atoms using laser light close to the D1 transition. First, a new compressed-MOT configuration is taking advantage of gray-molasses-type cooling induced by blue-detuned D1 light. It yields an optimized density of atoms. Then, we use pure D1 gray molasses to further cool the atoms to an ultra-low temperature of 6\\ \\mu\\text{K} . The resulting phase-space density is 2\\times 10^{-4} and will ease future experiments with ultracold potassium. As an example, we use it to directly load up to 3\\times 10^7 atoms in a far detuned optical trap, a result that opens the way to the all-optical production of potassium degenerate gases.

  1. EPR, ENDOR, and electronic structure studies of the Jahn-Teller distortion in an Fe(V) nitride.

    Cutsail, George E; Stein, Benjamin W; Subedi, Deepak; Smith, Jeremy M; Kirk, Martin L; Hoffman, Brian M

    2014-09-01

    The recently synthesized and isolated low-coordinate Fe(V) nitride complex has numerous implications as a model for high-oxidation states in biological and industrial systems. The trigonal [PhB((t)BuIm)3Fe(V)≡N](+) (where (PhB((t)BuIm)3(-) = phenyltris(3-tert-butylimidazol-2-ylidene)), (1) low-spin d(3) (S = 1/2) coordination compound is subject to a Jahn-Teller (JT) distortion of its doubly degenerate (2)E ground state. The electronic structure of this complex is analyzed by a combination of extended versions of the formal two-orbital pseudo Jahn-Teller (PJT) treatment and of quantum chemical computations of the PJT effect. The formal treatment is extended to incorporate mixing of the two e orbital doublets (30%) that results from a lowering of the idealized molecular symmetry from D3h to C3v through strong "doming" of the Fe-C3 core. Correspondingly we introduce novel DFT/CASSCF computational methods in the computation of electronic structure, which reveal a quadratic JT distortion and significant e-e mixing, thus reaching a new level of synergism between computational and formal treatments. Hyperfine and quadrupole tensors are obtained by pulsed 35 GHz ENDOR measurements for the (14/15)N-nitride and the (11)B axial ligands, and spectra are obtained from the imidazole-2-ylidene (13)C atoms that are not bound to Fe. Analysis of the nitride ENDOR tensors surprisingly reveals an essentially spherical nitride trianion bound to Fe, with negative spin density and minimal charge density anisotropy. The four-coordinate (11)B, as expected, exhibits negligible bonding to Fe. A detailed analysis of the frontier orbitals provided by the electronic structure calculations provides insight into the reactivity of 1: JT-induced symmetry lowering provides an orbital selection mechanism for proton or H atom transfer reactivity. PMID:25137531

  2. Comparative investigation of 39K and 40K trap loss rates alternative loss channel at low light intensities

    Modugno, G; Inguscio, M; Dos Santos, M S; Telles, G D; Marcassa, L G; Bagnato, V S

    2001-01-01

    We report a comparative investigation of trap loss rates in a magneto-optical trap for two potassium isotopes, 39K and 40K, as a function of trap light intensity. The isotopes present a quite similar behavior for the loss rates at high intensities, and a sudden increase of the loss rates at low intensities is present in both cases. While for 39K such increase can be explained assuming that the major contribution to the losses comes from Hyperfine Changing Collisions, a different loss mechanism must be considered for 40K, which has an inverted ground state hyperfine structure. The experimental results of both isotopes are well reproduced by an alternative model based on radiative escape as the dominant loss mechanism.

  3. Spin-mapping of coal structures with ESE and ENDOR

    Belford, R.L.; Clarkson, R.B.

    1990-12-01

    To ENDOR and ESE we have added another advanced EPR technique. VHF-EPR, as a tool with which to observe coal molecular structure, especially organic sulfur. We have constructed a unique VHF EPR instrument operating at the W-band (96 Ghz), one of only two such instruments in the world, and the only one studying coal. We are employing this instrument, as well as collaborating with scientists at Cornell University, who have a 250 GHz spectrometer, to develop a clearer understanding of the relationships between the VHF EPR spectra we observe from Illinois coal and the organic sulfur species present in it. Efforts in this quarter focussed on three area: recruitment of personnel (especially a new postdoctoral fellow) to join the coal research team work on improving the W-band spectrometer, and studies of vitrinite, sporinite, and fusinite macerals at G-band (250 GHz). All three areas have shown good progress. This report will discuss in detail the main features of the W-band instrument, stressing its unique engineering features as well as comparing it to the few other instruments in the world operating in the VHF frequency range (90--250 GHz). Preliminary analysis of the 250 GHz data on macerals obtained by density gradient centrifugation from an Illinois {number sign}6 coal gives the first indication that at the very highest frequencies, there may be a separation of the heteroatom VHF EPR signals into a sulfur and on oxygen-containing component. 15 refs., 9 figs., 1 tab.

  4. ENDOR study of VO/sup 2 +/-imidazole complexes in frozen aqueous solution

    Mulks, C.F.; Kirste, B.; van Willigen, H.

    1982-11-03

    Complexes formed between the oxovanadium(IV) cation and imidazole, carnosine, and histidine have been studied with ENDOR. It is shown that the technique gives information on proton and nitrogen hyperfine coupling components as well as /sup 14/N quadrupole splittings. The data provide insight into the geometric structure of the complexes. The results presented indicate that ENDOR studies of VO/sup 2 +/ binding to more complex systems of biological interest (such as proteins) can be used to identify binding to histidine moieties. Furthermore, such studies could be of help in establishing the binding site geometry.

  5. Spin-mapping of coal structures with ESE and ENDOR

    Belford, R.L.; Clarkson, R.B.

    1990-09-01

    A nondestructive method to determine the atomic and molecular structures present in the organic (maceral) components of whole coal and coal products has been sought for many years. This program of research is designed to address that analytical need by applying advanced electron magnetic resonance techniques to the determination of coal molecular structure. Structural information has be obtained by using the naturally occurring unpaired electrons in coal as observation posts'' from which to survey neighboring atoms through the electron-nuclear hyperfine interaction. Such an overall approach has been termed ELECTRON SPIN MAPPING of coal structure. New techniques like 2-dimensional ENDOR and ESE spectroscopies and multifrequency EPR, including the world's first S-band ESE spectrometer and one of the first W-band instruments, which we have developed in our laboratory, were employed in the determination. The materials studied were well separated macerals obtained by density gradient centrifugation techniques from Illinois {number sign}6 coals, a well as whole Illinois {number sign}6, {number sign}5, and Argonne Premium Sample Coals. model compounds, chosen to represent molecular structures typical of those believed to exist in coal also were studied by the various electron magnetic resonance (EMR) methods. Utilizing the various EMR methods available in our laboratory, we studied approaches to determine parameters that direcly reflect the atomic and molecular structure of coal. The naturally occurring unpaired electrons in coal were utilized as probes of their local environment, which they reflect through hyperfine interactions with neighboring 1 > 0 nuclei (eg, {sup 1}H, {sup 13}C).

  6. High-frequency EPR and ENDOR spectroscopy on semiconductor quantum dots

    Baranov, P.G.; Orlinskii, S.B.; de Mello Donega, C.; Schmidt, J.

    2010-01-01

    It is shown that high-frequency electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy are excellent tools for the investigation of the electronic properties of semiconductor quantum dots (QDs). The great attractions of these techniques are that, in contrast

  7. Spectroscopy of the Double Minimum $3\\,^3 \\Pi_{\\Omega}$ Electronic State of $^{39}$K$^{85}$Rb

    Banerjee, Jayita; Carollo, Ryan; Bellos, Michael; Eyler, Edward E; Gould, Phillip L; Stwalley, William C

    2013-01-01

    We report the observation and analysis of the $3\\,^3\\Pi_{\\Omega}$ double-minimum electronic excited state of $^{39}$K$^{85}$Rb. The spin-orbit components ($0^{+}, 0^{-}, 1$ and 2) of this state are investigated based on potentials developed from the available \\emph{ab initio} potential curves. We have assigned the vibrational levels $v'=2-11$ of the $3\\,^3\\Pi_{1,2}$ potentials and $v'=2-12$ of the $3\\,^3\\Pi_{0^{+/-}}$ potential. We compare our experimental observations of the $3\\,^3\\Pi_{\\Omega}$ state with predictions based on theoretical potentials. The observations are based on resonance enhanced multiphoton ionization (REMPI) of ultracold KRb in vibrational levels $v"=14-25$ of the $a\\,^3\\Sigma^+$ state. These \\emph{a}-state ultracold molecules are formed by photoassociation of ultracold $^{39}$K and $^{85}$Rb atoms to the 5(1) state of KRb followed by spontaneous emission to the \\emph{a} state.

  8. Matrix ENDOR of the protonated carboxylic anion radical in γ-irradiated l-alanine. Simulation using a general matrix ENDOR line-shape model and single crystal data

    The matrix ENDOR line from the CH3CH(+NH3)COOOH- radical in γ-irradiated L-alanine powder at 77 K was simulated by using a generalized matrix ENDOR line-shape theory. The input includes hyperfine coupling constants for all protons in the proximity of the radical site as well as the pure dipolar interaction for more distant protons, microwave and radio-frequency magnetic field magnitudes, and nuclear and electron spin-lattice and spin-spin relaxation times. Simulated matrix ENDOR lines were tested against experimental line shapes, line widths, and the intensity of the ENDOR response as a function of the radio-frequency magnetic field. The simulated ENDOR response was found to be very sensitive to the value of the nuclear spin-lattice relaxation time, and a value of 0.15 s satisfactorily reproduces the experimental results. The relevant conclusion from this study is that an angularly independent nuclear relaxation mechanism dominates the ENDOR response

  9. Natural and induced endoreic hydrological conditions in the Alta Murgia karstic region (Apulia, Southern Italy)

    Canora, F.; Fidelibus, M. D.; Spilotro, G.

    2009-04-01

    A study aimed at understanding the hydrological processes in karst areas related to the presence of natural and artificial endoreic basins and their modification due to land use change, as well as the influence of above factors on the infiltration rate has been carried out in the Alta Murgia region (Apulia, Southern Italy). The region is a Cretaceous limestone plateau of the Apulian platform, characterized by a mature karstic landscape: due to its elevation, climatic conditions and lithology, the plateau constitutes the main recharge area of the Murgia aquifer. The typical karst topography is essentially related to the subterranean drainage (sinkholes, caves, conduit): surface and subsurface karst geomorphology is strictly interrelated with hydrology. The morphological features of the karstic plateau are defined by the high density of surface karstic forms (mainly dolines), the presence of exposed karst and karren fields, as well as by the extensive outcrop of fractured rocks. Karst surface shows, on the bottom of the morpho-structural depressions called "lame", natural distribution of modest deposits of "terra rossa" and regolith. The "lame" work as streams during and after intense rainfall events, often outlining a primordial ephemeral hydrographical network, frequently convergent towards dolines, poljes or endoreic basins. Alta Murgia shows many natural endoreic basin conditions in a quite flat morphology. In this environment, when intense rainfall events cover large areas and rainfall intensity exceeds the infiltration capacity of soils and/or sinkholes, significant runoff amounts are produced and stored in the basins causing floods. Most of the natural endoreic basins are small and independent: while the majority of them continue functioning as endoreic even in presence of extreme events of high return time, others (quasi-endoreic), under the same circumstances can start contributing to other basins, due to exceeding their water storage capability. This way

  10. Efimov studies of an ultracold cloud of 39 K atoms in microgravity: Numerical modelling and experimental design

    Mossman, Maren; Engels, Peter; D'Incao, Jose; Jin, Deborah; Cornell, Eric

    2016-05-01

    Ultracold atomic gases at or near quantum degeneracy provide a powerful tool for the investigation of few-body physics. A particularly intriguing few-body phenomenon is the existence of Efimov trimer states at large interatomic scattering lengths. These trimers are predicted to exhibit universal geometric scaling relations, but in practice the situation is complicated e.g. by finite-range and finite-temperature effects. While some Efimov trimers have already been experimentally observed by several groups in ground-based experiments, NASA's Cold Atom Laboratory (CAL) onboard the ISS will greatly enhance the experimentally accessible regimes by providing ultracold clouds of 39 K atoms with temperatures at or below 1 nK, low densities, and long observation times. We present results of numerical modelling and simulations that lay out Efimov experiments capitalizing on the particular strengths of CAL.

  11. Domain configurations in the ferroelectric phase of KH2AsO4 from ENDOR studies of irradiated crystals

    Using ENDOR spectroscopy, the radical AsO44- created by gamma irradiation in KH2AsO4 crystals has been reexamined. An earlier study by Dalal et al. had shown the existence of two types of domains in the ferro-electric phase. By considering the origin of a small splitting of the ENDOR lines, it is shown that in fact this technique allows the detection of the four domain types which are expected to exist in KH2AsO4 as in KH2PO4

  12. An ENDOR spectrum of H atoms in solid H{sub 2}

    Kumada, Takayuki; Kumagai, J.; Aratono, Yasuyuki; Miyazaki, T. [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Kitagawa, N.; Noda, T.

    1998-10-01

    An ENDOR spectrum of H atoms produced in the {gamma}-rays irradiated solid H{sub 2} was measured at 4.2 K in order to elucidate the structures of the local environment of the H atoms in solid H{sub 2}. We found that the H atoms were not trapped in interstitial sites but in substitutional sites of the solid, and almost all ortho-H{sub 2} molecules at the first nearest sites from the H atoms converted into para-H{sub 2} molecules. This result shows that the ortho-para conversion is induced by electron spins of the H atoms. (author)

  13. ESR/ENDOR study of the guanine cation: Secondary product in 5' -dGMP

    Previous ESR studies by Voit and Huttermann of x-irradiated single crystals of 2' deoxyguanosine-5'-monophosphate have indicated the presence of a radical thought to be formed by deprotonation of the primary base cation at N1. In this study the authors report results of a detailed ESR and ENDOR experiment at 10 K which conflict with the results cited above. One of the radicals detected inhibited two α-proton type couplings. The data analysis shows that one coupling is due to the proton on the extra annular NH/sub 2/ group, while the other is due to the proton bonded to C8

  14. ESR and ENDOR studies of radiation damage in some x-irradiated biological molecules

    ESR and ENDOR spectroscopy were used to observe the effects of ionizing radiations on single crystals of 1-methyl cytosine, glycylglycine HNO3, histidine HNO3, and glycine AgNO3. Various primary, secondary and final radicals were observed and identified in these single crystals by magnetic resonance techniques. In 1-methyl cytosine, irradiated at room temperature, two hydrogen addition free radicals were characterized using ENDOR. In partially deuterated crystals of glycylglycine DNO3, on x-irradiation at 4.20K, NO32- was observed as the primary reduction product and NO2 as the secondary reduction product. The most interesting result of the study has been to show how the presence of the NO3- ion determines the course of the reduction process initiated by ionizing radiations. A mechanism for the formation of the secondary reduction product NO2 from the primary reduction product NO32- has also been inferred from these experiments. In glycylglycine HNO3 crystals grown from water, on x-irradiation at 4.20K, only the secondary reduction product is observed indicating that transformation from NO32- to NO2 is complete at 4.20K. In amino acid salt histidine HNO3, x-irradiation at 4.20K produces the paramagnetic species NO32- and NO2, respectively the primary and secondary reduction products. The capacity of NO3- ions to scavenge electrons can be clearly demonstrated. s. Abstr. Int., B)

  15. Direct ionization effects of purine derivatives: ESR and ENDOR studies of 5'GMP

    In this study the free acid of 5' GMP was investigated (in the form of 5'GMP.3H/sub 2/O crystals). Irradiation and study of the molecular system below 10K gave evidence for at least three products in the ESR. Product I was also studied by ENDOR, and has been tentatively identified as the result of the anion protonated at 06. From the experimental data the spin distribution in product I is: 30% at C8; 12% at N1; 10% at N7. Product II was identified from its characteristic ESR as the result of hydrogen addition at C8. Product III was evident in the ESR but has not yet been identified

  16. Free radical formation in crystals of guanine hydrochloride dihydrate: an ESR and ENDOR study

    Radiation-induced free radical formation in single crystals of guanine hydrochloride dihydrate has been studied at temperatures between 20 and 300 K using ESR and ENDOR spectroscopy. At low temperatures three radical species are trapped. Two of these are the C8 H-addition radical R1 previously analysed by Alexander and Gordy (1967) and the O6-protonated anion radical R2. The third species (R4) remains unidentified. Upon annealing at 280 K for an extended period the protonated anion R2 transforms into a new radical R3 which exhibits a well-defined hyperfine pattern but still could not be identified unambiguously. Also radical R4 probably transforms into a new radical (R5) upon such treatment. One proton coupling due to R5 was detected. A scheme of radical reactions incorporating these five radicals is proposed. This scheme also suggests that differences in radical formation between the monohydrate and dihydrate crystals of guanine hydrochloride depends upon differences in the hydrogen bonding network. (author)

  17. No evidence of a death-like function for species B1 human adenovirus type 3 E3-9K during A549 cell line infection

    Frietze Kathryn M

    2012-08-01

    Full Text Available Abstract Background Subspecies B1 human adenoviruses (HAdV-B1 are prevalent respiratory pathogens. Compared to their species C (HAdV-C counterparts, relatively little work has been devoted to the characterization of their unique molecular biology. The early region 3 (E3 transcription unit is an interesting target for future efforts because of its species-specific diversity in genetic content among adenoviruses. This diversity is particularly significant for the subset of E3-encoded products that are membrane glycoproteins and may account for the distinct pathobiology of the different human adenovirus species. In order to understand the role of HAdV-B-specific genes in viral pathogenesis, we initiated the characterization of unique E3 genes. As a continuation of our efforts to define the function encoded in the highly polymorphic ORF E3-10.9K and testing the hypothesis that the E3-10.9K protein orthologs with a hydrophobic domain contribute to the efficient release of viral progeny, we generated HAdV-3 mutant viruses unable to express E3-10.9K ortholog E3-9K and examined their ability to grow, disseminate, and egress in cell culture. Results No differences were observed in the kinetics of infected cell death, and virus progeny release or in the plaque size and dissemination phenotypes between cells infected with HAdV-3 E3-9K mutants or the parental virus. The ectopic expression of E3-10.9K orthologs with a hydrophobic domain did not compromise cell viability. Conclusions Our data show that despite the remarkable similarities with HAdV-C E3-11.6K, HAdV-B1 ORF E3-10.9K does not encode a product with a “death-like” biological activity.

  18. Radiation damage in vitamin B1: an ENDOR study of an x-irradiated single crystal of thiamine

    A single crystal of thiamine chloride hydrochloride has been x-irradiated at room temperature and studied by 1H-ENDOR spectroscopy at 110 K. It is shown that at least two radical species are trapped in the crystal. Several 1H-hyperfine tensors have been determined for each radical; they indicate that one species is due to cleavage of the thiamine molecule into its pyrimidine and thiazole moieties while the other species is due to hydrogen addition onto the pyrimidine ring. (author)

  19. Spin-mapping of coal structures with ESE and ENDOR. Eighth quarterly (second annual) report

    Belford, R.L.; Clarkson, R.B.

    1990-09-01

    A nondestructive method to determine the atomic and molecular structures present in the organic (maceral) components of whole coal and coal products has been sought for many years. This program of research is designed to address that analytical need by applying advanced electron magnetic resonance techniques to the determination of coal molecular structure. Structural information has be obtained by using the naturally occurring unpaired electrons in coal as ``observation posts`` from which to survey neighboring atoms through the electron-nuclear hyperfine interaction. Such an overall approach has been termed ELECTRON SPIN MAPPING of coal structure. New techniques like 2-dimensional ENDOR and ESE spectroscopies and multifrequency EPR, including the world`s first S-band ESE spectrometer and one of the first W-band instruments, which we have developed in our laboratory, were employed in the determination. The materials studied were well separated macerals obtained by density gradient centrifugation techniques from Illinois {number_sign}6 coals, a well as whole Illinois {number_sign}6, {number_sign}5, and Argonne Premium Sample Coals. model compounds, chosen to represent molecular structures typical of those believed to exist in coal also were studied by the various electron magnetic resonance (EMR) methods. Utilizing the various EMR methods available in our laboratory, we studied approaches to determine parameters that direcly reflect the atomic and molecular structure of coal. The naturally occurring unpaired electrons in coal were utilized as probes of their local environment, which they reflect through hyperfine interactions with neighboring 1 > 0 nuclei (eg, {sup 1}H, {sup 13}C).

  20. Protonation/deprotonation processes of primary products in x-irradiated cytosine derivatives: EPR and ENDOR studies at 10 K

    Recently, evidence has accumulated that cytosine is the initial electron trap in irradiated DNA. It has previously been observed that the protonation/deprotonation mechanisms and sites of the pristine purine/pyrimidine electron gain and loss centers depend upon the matrix. Local variations as e.g. water of crystallization, hydrogen bond pattern, initial protonation state of the cytosine bases, and associated counter ions may be important in the selection of reaction pathways following the initial ionization event. In response to this increased interest in the primary radical production in irradiated cytosine, five different crystalline cytosine derivatives have been investigated at 10 K following X-irradiation exposure to doses between 0.8 and 30 kGy. The techniques used are K-band EPR, ENDOR, and ENDOR-induced EPR (FSE) spectroscopy. The systems studied are: cytosine monohydrate (Cm); cytosine-HCI (C:HCl); cytidine (CR); deoxycytidine:HCI (CdR:HCl); and 2'-deoxycytidine 5'-monophosphate (5'dCMP)

  1. Free radical products in X-irradiated Rochelle salt: low temperature ENDOR and DFT studies

    Single crystals of Rochelle salt, [−OOC–CHOH–CHOH–COO−, Na+, K+]·4H2O, X-irradiated at 10 K, have been examined using EPR, ENDOR and EIE spectroscopic techniques to characterize the radiation induced radicals stable at that temperature and their reactions upon warming. The one-electron gain product was observed and from the hyperfine interaction with a β-proton it was unambiguously centered at the C4 position of the tartrate moiety. An additional nearly isotropic hyperfine structure of about 21 MHz was tentatively assigned to interaction with a sodium ion exhibiting a close contact to O3 in the crystal. Evidence was obtained that the one-electron reduced radical had become protonated at one of the C4 bonded carboxyl oxygens, most probably O4. No evidence for the corresponding C1-centered reduction product was found. Two resonance lines (R2, A1) were shown by EIE to belong to a species formed by decarboxylation at C3, a secondary oxidation product. Two other resonance lines (K1, K2) were assigned to two varieties of another decarboxylation radical, centered at C2, distinguished by differences in the potassium ion coordination. Furthermore, one other resonance line (A2) was tentatively ascribed to a third decarboxylation radical, centered at the opposite end of the tartrate moiety. The precursor of these products, that is, the one-electron loss product, was not observed after X-irradiation at 10 K. Thermally induced free radical reactions followed by EPR in the temperature range of 12–119 K indicate that a water molecule or a hydroxyl ion is eliminated from the one-electron reduction product radical and that a C3-centered radical is formed. The reduction and oxidation reaction pathways of hydroxy acid derivatives are discussed. - Highlights: ► Crystalline Rochelle salt was X-irradiated at 10 K and studied using EMR techniques. ► Interpretation of present and previous data was aided by cluster DFT calculations. ► Regioselective reduction and non

  2. A single-crystal proton ENDOR study of the ClO3 centre in γ-irradiated barium perchlorate at 120 K

    Hyperfine coupling tensors for 24 protons have been determined from electron nuclear double resonance (ENDOR) measurements of the C1O3 centre trapped in γ-irradiated single crystals of barium perchlorate trihydrate at 120 K. The tensors have small isotropic components and their dipolar components are close to axial so that their interpretation in the point-dipole approximation to reconstruct the proton geometry in the vicinity of the trapped radical is justifiable. The model thus obtained indicates that there is no severe distortion of the crystal structure in the immediate vicinity of the trapped radicals. There are two chemically identical but ENDOR-distinguishable sites related by a reflection in the a1a2 plane of the hexagonal crystal. The observation supports the assignment of the P63/m space group to the crystal. (author)

  3. Electron spin resonance and E.N.D.O.R. double resonance study of free radicals produced by gamma irradiation of imidazole single crystals

    Gamma irradiation of imidazole single crystals at 300 deg. K gives two radicals. Identification and detailed studies of their electronic and geometric structure have been made by ESR and ENDOR techniques. A study of the hydrogen bonded protons hyperfine tensor is made and let us conclude to the inexistence of movement and tunneling of these protons. The principal low temperature radical, produced by gamma irradiation at 77 deg. K has been also studied by ESR and a model has been proposed. (author)

  4. Mo(V) co-ordination in the periplasmic nitrate reductase from Paracoccus pantotrophus probed by electron nuclear double resonance (ENDOR) spectroscopy.

    Butler, Clive S; Fairhurst, Shirley A; Ferguson, Stuart J; Thomson, Andrew J; Berks, Ben C; Richardson, David J; Lowe, David J

    2002-05-01

    The first electron nuclear double resonance (ENDOR) study of a member of the Mo-bis-molybdopterin guanine dinucleotide family of molybdoenzymes is presented, using the periplasmic nitrate reductase from Paracoccus pantotrophus. Rapid freeze-quenched time-resolved EPR revealed that during turnover the intensity of a Mo(V) EPR signal known as High-g [resting] increases. This signal is split by two interacting protons that are not solvent-exchangeable. X-band proton-ENDOR analysis resolved broad symmetrical resonance features that arose from four classes of protons weakly coupled to the Mo(V). Signals from two of these were lost upon exchange into deuterated buffer, suggesting that they may originate from OH(-) or H(2)O groups. One of these signals was also lost when the enzyme was redox-cycled in the presence of azide. Since these protons are very weakly coupled OH/H(2)O groups, they are not likely to be ligated directly to the Mo(V). This suggests that protonation of a Mo(VI)zO group does not occur on reduction to Mo(V), but most probably accompanies reduction of Mo(V) to Mo(IV). A resonance feature from a more strongly coupled proton, that was not lost following exchange into deuterated buffer, could also be resolved at 22-24 MHz. The anisotropy of this feature, determined from ENDOR spectra collected at a range of field positions, indicated a Mo-proton distance of approx. 3.2 A, consistent with this being one of the beta-methylene protons of a Mo-Cys ligand. PMID:11964184

  5. Anisotropic Fermi Couplings due to Large Unquenched Orbital Angular Momentum: Q-band 1H, 14N and 11B ENDOR of bistrispyrazolylborate Co(II)

    Myers, William K.; Scholes, Charles P.; Tierney, David L.

    2009-01-01

    We report Q-band ENDOR of 1H, 14N, and 11B at the g|| extreme of the EPR spectrum of bistrispyrazolylborate Co(II), Co(Tp)2 and two structural analogs. This trigonally symmetric, high-spin (hs) S = 3/2 Co(II) complex shows large unquenched ground–state orbital angular momentum, which leads to highly anisotropic electronic g-values [g|| = 8.48, g⊥ = 1.02]. The large g-anisotropy is shown to result in large dipolar couplings near g|| and uniquely anisotropic 14N Fermi couplings, which arise from spin transferred to the nitrogen 2s orbital (2.2 %) via anti-bonding interactions with singly occupied metal dx2−y2 and dz2 orbitals. Large, well-resolved 1H and 11B dipolar couplings were also observed. Taken in concert with our previous X-band ENDOR measurements at g⊥ (Myers, et al, Inorg. Chem. 2008, 47, 6701–6710), the present data allow a detailed analysis of the dipolar hyperfine tensors of two of the four symmetry distinct protons in the parent molecule. In the substituted analogs, changes in hyperfine coupling due to altered metal-proton distances give further evidence of an anisotropic Fermi contact interaction. For the pyrazolyl 3H proton, the data indicate a 0.2 MHz anisotropic contact interaction and ~ 4 % transfer of spin away from Co(II). Dipolar coupling also dominates for the axial boron atoms, consistent with their distance from the Co(II) ion, and resolved 11B quadrupolar coupling showed ~ 30 % electronic inequivalence between the B-H and B-C sp3 bonds. This is the first comprehensive ENDOR study of any hs Co(II) species and lays the foundation for future development. PMID:19591466

  6. Hydrochemical Differentiation of Salinisation Process of the Water in Endoreic Semi-Arid Basin: Case of Rémila Basin, Algeria

    Houha Belgacem; Kherici Nacer; Kachi Slimane; Valles Vincent

    2008-01-01

    The aim of this study is to determine and treat a hierarchical basis of the various mechanisms responsible for the space variation of the water quality in a endoreic semi-arid basin. The water chemistry showed a large variability in space and time. The total dissolved solid (TDS) in water increases from upstream to downstream due to the effect of the arid climate, but also due to the water-rock interactions and the anthropic polution of surface water. The water chemistry changes progressively...

  7. EPR, ENDOR and DFT study of L-lysine·HCl·2H 2O single crystals X-irradiated at 66 K

    Zhou, Yiying; Nelson, William H.

    2010-04-01

    Electron Paramagnetic Resonance (EPR), Electron-Nuclear DOuble Resonance (ENDOR) and ENDOR-Induced EPR (EIE) results indicated at least three radicals produced in L-lysine·HCl·2H 2O crystals irradiated at 66 K. EPR from radical R1 dominated the spectra and it was identified as the carboxyl anion, (H 2OOĊ) CH (NH 3) + (CH 2) 4 (NH 3) +. Density-Functional Theory (DFT) calculations supported the assignment and indicated that the carboxyl group transformed from planar to a pyramidal configuration following electron trapping. Two small couplings detected from R1 were ascribed to protons transferred to the carboxyl group from neighboring molecules through intermolecular hydrogen bonds. Radical R2 was identified as the product of decarboxylation, ĊH (NH 3) +(CH 2) 4 (NH 3) +. Although it was not possible to obtain R2's α-coupling tensor from the experiment, EPR simulations and DFT calculations provided strong support for the identification. Radical R3 exhibited several β-couplings but could be detected only in one plane and could not be identified.

  8. EPR, ENDOR and DFT study of L-lysine.HCl.2H2O single crystals X-irradiated at 66 K

    Electron Paramagnetic Resonance (EPR), Electron-Nuclear DOuble Resonance (ENDOR) and ENDOR-Induced EPR (EIE) results indicated at least three radicals produced in L-lysine.HCl.2H2O crystals irradiated at 66 K. EPR from radical R1 dominated the spectra and it was identified as the carboxyl anion, (H2OOC) CH (NH3)+ (CH2)4 (NH3)+. Density-Functional Theory (DFT) calculations supported the assignment and indicated that the carboxyl group transformed from planar to a pyramidal configuration following electron trapping. Two small couplings detected from R1 were ascribed to protons transferred to the carboxyl group from neighboring molecules through intermolecular hydrogen bonds. Radical R2 was identified as the product of decarboxylation, CH (NH3)+(CH2)4 (NH3)+. Although it was not possible to obtain R2's α-coupling tensor from the experiment, EPR simulations and DFT calculations provided strong support for the identification. Radical R3 exhibited several β-couplings but could be detected only in one plane and could not be identified.

  9. EPR and ENDOR characterization of the reactive intermediates in the generation of NO by cryoreduced oxy-nitric oxide synthase from Geobacillus stearothermophilus.

    Davydov, Roman; Sudhamsu, Jawahar; Lees, Nicholas S; Crane, Brian R; Hoffman, Brian M

    2009-10-14

    Cryoreduction EPR/ENDOR/step-annealing measurements with substrate complexes of oxy-gsNOS (3; gsNOS is nitric oxide synthase from Geobacillus stearothermophilus) confirm that Compound I (6) is the reactive heme species that carries out the gsNOS-catalyzed (Stage I) oxidation of L-arginine to N-hydroxy-L-arginine (NOHA), whereas the active species in the (Stage II) oxidation of NOHA to citrulline and HNO/NO(-) is the hydroperoxy-ferric form (5). When 3 is reduced by tetrahydrobiopterin (BH4), instead of an externally supplied electron, the resulting BH4(+) radical oxidizes HNO/NO(-) to NO. In this report, radiolytic one-electron reduction of 3 and its complexes with Arg, Me-Arg, and NO(2)Arg was shown by EPR and (1)H and (14,15)N ENDOR spectroscopies to generate 5; in contrast, during cryoreduction of 3/NOHA, the peroxo-ferric-gsNOS intermediate (4/NOHA) was trapped. During annealing at 145 K, ENDOR shows that 5/Arg and 5/Me-Arg (but not 5/NO(2)Arg) generate a Stage I primary product species in which the OH group of the hydroxylated substrate is coordinated to Fe(III), characteristic of 6 as the active heme center. Analysis shows that hydroxylation of Arg and Me-Arg is quantitative. Annealing of 4/NOHA at 160 K converts it first to 5/NOHA and then to the Stage II primary enzymatic product. The latter contains Fe(III) coordinated by water, characteristic of 5 as the active heme center. It further contains quantitative amounts of citrulline and HNO/NO(-); the latter reacts with the ferriheme to form the NO-ferroheme upon further annealing. Stage I delivery of the first proton of catalysis to the (unobserved) 4 formed by cryoreduction of 3 involves a bound water that may convey a proton from L-Arg, while the second proton likely derives from the carboxyl side chain of Glu 248 or the heme carboxylates; the process also involves proton delivery by water(s). In the Stage II oxidation of NOHA, the proton that converts 4/NOHA to 5/NOHA likely is derived from NOHA itself, a

  10. Imidazole π cation and barbital π anion trapped in a cocrystalline complex x-irradiated at 12 K: An ESR--ENDOR study

    The predominant free radicals trapped in single crystals of the 1:1 intermolecular complex of imidazole and 5,5-diethylbarbituric acid (barbital) x-irradiated at 12 K have been identified by ESR and ENDOR. The electron abstraction and electron addition products are found to be the imidazole π cation and the barbital π anion, respectively. The π cation provides experimental evidence of evenly distributed unpaired electron density at positions C2, C4, and C5 of the five membered imidazole ring. In the π anion the unpaired electron density is localized primarily on C4 of barbital. It is suggested that π anions are trapped in barbital in preference to imidazole because barbital has a higher cross section for electron capture than imidazole. On the other hand, π cations are trapped in imidazole in preference to barbital because the barbital π cation has a higher cross section for destruction than the imidazole π cation

  11. Free radicals in L-arginine·HCl·H2O single crystals X-irradiated at 298 K-EPR, ENDOR and DFT studies

    Electron Paramagnetic Resonance (EPR), Electron-Nuclear DOuble Resonance (ENDOR) and ENDOR Induced EPR (EIE) results indicated at least three radicals produced in L-arginine·HCl·H2O single crystals irradiated at 298 K. Radical RI dominated the central portion of the EPR spectra and was identified as the main-chain deamination radical, and Density Function Theory (DFT) calculations indicated that RI has protonated carboxyl group, (H2…OOC)ĊH(CH2)3 NHC(NH2)2+, and the COOH protons are transferred from the hydrogen bonded amino group and guanidyl group in two different neighboring molecules. Radicals RII and RIII were identified respectively as the radicals dehydrogenated at C5, −(OOC)CH(NH3)+(CH2)2ĊHNHC(NH2)2+, and at C2, −(OOC)Ċ(NH3)+(CH2)3NHC(NH2)2+. Two conformations of RII were detected, denoted as RIIa and RIIb, and the conformational differences are mainly due to the different dihedral angles of the two β-protons bonded to C4, which were supported by the modeling calculations for RIIa and RIIb. - Highlights: • Three distinct free radicals formed in X-ray irradiated L-arginine·HCl·H2O single crystals at 298 K were identified. • DFT modeling computations indicated the main-chain deamination radical has protonated carboxyl group. • Two conformations of the radical dehydrogenated at C5 were detected. The conformational differences were analyzed with experimental and computational methods. • The annealing experiments indicated these three radicals are stable radicals

  12. EPR, ENDOR, and HYSCORE study of the structure and the stability of vanadyl-porphyrin complexes encapsulated in silica: potential paramagnetic biomarkers for the origin of life.

    Gourier, Didier; Delpoux, Olivier; Bonduelle, Audrey; Binet, Laurent; Ciofini, Ilaria; Vezin, Hervé

    2010-03-18

    The possibility of using vanadyl ions as paramagnetic biomarkers for the identification of traces of primitive life fossilized in silica rocks is studied by cw-EPR, ENDOR, HYSCORE, and DFT calculations. It is well-known that porphyrins, which are common to all living organisms, form vanadyl-porphyrin complexes in sediments deposited in oceans. However, the stability of these complexes over a very long time (more than 3 billion years) is not known. By encapsulating vanadyl-porphyrin complexes in silica synthesized by a sol-gel method to mimic SiO(2) sediments, we studied the structure and stability of these complexes upon step heating treatments by monitoring the evolution of the g factor and of the hyperfine interactions with (51)V, (1)H, (14)N, (13)C, and (29)Si nuclei. It is found that vanadyl-porphyrin complexes are progressively transformed into oxygenated vanadyl complexes by transfer of the VO(2+) ion from the porphyrin ring to the mineral matrix. The organic component is transformed into carbonaceous matter which contains paramagnetic centers (IOM(*) centers). To test the validity of this approach, we studied by EPR a 3490 million years old chert (polycrystalline SiO(2) rock) containing some of the oldest putative traces of life. This rock contains oxygenated vanadyl complexes and IOM(*) centers very similar to those found in the synthetic analogues. PMID:20175553

  13. Electron spin-resonance (ESR) and electron-nuclear double-resonance (ENDOR) study of the self-trapped hole in ZnWO4 single crystals

    After x-ray irradiation at 20 K, an intrinsic O- centre was identified by ESR and ENDOR spectroscopy as the self-trapped hole centre in ZnWO4. Observation of one Zn and two strong W superhyperfine interactions allows us to distinguish between two possible trapping sites: the hole resides at the B-type oxygen position which has one Zn and two W nearest neighbours. Broadening of the ESR lines and averaging of the g-value is observed and explained as due to thermally activated hopping of the hole between two energetically equivalent oxygen positions. The activation energy of this reorientation is found to be 0.016±0.003 eV. The thermal decay of the intrinsic O- centre, and its connection to thermoluminescence, has been studied; it shows that this centre cannot be the luminescence centre for the typical TL emission at ∼480 nm in ZnWO4. This emission may be due to an intrinsic electron-type defect. (author)

  14. EPR, Endor and DFT Studies on X-Irradiated Single Crystals of L-Lysine HCl 2 H 2O and L-Arginine HCl H2O

    Zhou, Yiying; Nelson, William H.

    2011-03-01

    When proteins and DNA interact, arginine and lysine are the two amino acids most often in close contact with the DNA. In order to understand the radiation damage to DNA in vivo, which is always associated with protein, it is important to learn the radiation chemistry of arginine and lysine independently, and then complexed to DNA. This work studied X-irradiated single crystals of L- lysine . HCl . 2 H2 O and L- arginine . HCl . H2 O with EPR, ENDOR techniques and DFT calculations. In both crystal types irradiated at 66K, the carboxyl anion radical and the decarboxylation radical were identified. Specifically, the calculations performed on the cluster models for the carboxyl anion radicals reproduced the proton transfers to the carboxyl group from the neighboring molecules through the hydrogen bonds. Moreover, computations supported the identification of one radical type within irradiated arginine as the guanidyl radical anion with an electron trapped by the guanidyl group. Based on the radicals detected in the crystal irradiated at 66K and at 298K, and the annealing experiments from the irradiation at 66K, the mechanisms of the irradiation damage on lysine and arginine were proposed, and the possible effects of irradiated arginine and lysine to the DNA within chromatin were analyzed.

  15. Hydrochemical Differentiation of Salinisation Process of the Water in Endoreic Semi-Arid Basin: Case of Rémila Basin, Algeria

    Houha Belgacem

    2008-01-01

    Full Text Available The aim of this study is to determine and treat a hierarchical basis of the various mechanisms responsible for the space variation of the water quality in a endoreic semi-arid basin. The water chemistry showed a large variability in space and time. The total dissolved solid (TDS in water increases from upstream to downstream due to the effect of the arid climate, but also due to the water-rock interactions and the anthropic polution of surface water. The water chemistry changes progressively from bicarbonate calcic upstream to sulphated and chlorinated calcic in the median zone to chlorinate sodic in the Sebkha. Thermodynamic modelling showed the major role of evaporation in the evolution of the water chemistry. The result indicated calcite precipitation then gypsum precipitation as well as cations exchanges reactions. Statistical approach allowed to arrange processes that responsible for the hydrochemical variability according to their important. The increase of water salinity is due mainly to the aridity process. The differentiation between salty surface water (Sebkha and deeper water (Chott is the second process. The combined of the geochemical and statistical methods allowed to identify the main

  16. Interaction of Cr3+ with valence and conduction bands in the long persistent phosphor ZnGa2O4:Cr3+, studied by ENDOR spectroscopy

    Binet, Laurent; Sharma, Suchinder K.; Gourier, Didier

    2016-09-01

    Cr3+-doped zinc gallate ZnGa2O4 is a red-near infrared (IR) long persistent phosphor that can be excited by orange-red light, in the transparency window of living tissues. With this property, persistent luminescence nanoparticles were recently used for in vivo optical imaging of tumors in mice. In order to understand the origin of the excitability of persistent luminescence by visible light in this material, a Q-band ENDOR investigation of 71/69Ga and 53Cr nuclei was performed in ZnGa2O4:Cr3+ to get information on the interaction of Cr3+ with valence and conduction bands. The positive electron spin density at Ga nuclei revealed a dominant interaction of the 4A2 ground state of Cr3+ with the valence band, and a weaker interaction with the conduction band. The latter may occur only in the excited 2E and 4T2 states of Cr3+. It is proposed that when these two interactions are present, pairs of electrons and holes can be generated from excited Cr3+ in distorted sites undergoing local electric field produced by neighboring defects with opposite charges.

  17. Strong resistance of Arabidopsis thaliana and Raphanus sativus seeds for ionizing radiation as studied by ESR, ENDOR, ESE spectroscopy and germination measurement: Effect of long-lived and super-long-lived radicals

    Resistance of seeds for ionizing radiation effects on Arabidopsis thaliana and Raphanus sativus seeds were investigated by ESR, ENDOR, ESE spectroscopy and germination measurement. Two types of free radicals, such as long-lived (LL) and super-long-lived (SL) radicals, were produced by the γ-irradiation in the seeds. More than 90% of the 1 kGy-irradiated-seeds can germinate probably by decreasing the LL radicals by absorbing water. 10 kGy-irradiated-seeds cannot germinate at all probably due to the existence of significant amounts of the SL radicals even after absorbing water. (author)

  18. Strong resistance of Arabidopsis thaliana and Raphanus sativus seeds for ionizing radiation as studied by ESR, ENDOR, ESE spectroscopy and germination measurement: Effect of long-lived and super-long-lived radicals

    Kumagai, Jun E-mail: kumagai@apchem.nagoya-u.ac.jp; Katoh, Hiromi; Kumada, Takayuki; Tanaka, Atsushi; Tano, Shigemitsu; Miyazaki, Tetsuo

    2000-01-01

    Resistance of seeds for ionizing radiation effects on Arabidopsis thaliana and Raphanus sativus seeds were investigated by ESR, ENDOR, ESE spectroscopy and germination measurement. Two types of free radicals, such as long-lived (LL) and super-long-lived (SL) radicals, were produced by the {gamma}-irradiation in the seeds. More than 90% of the 1 kGy-irradiated-seeds can germinate probably by decreasing the LL radicals by absorbing water. 10 kGy-irradiated-seeds cannot germinate at all probably due to the existence of significant amounts of the SL radicals even after absorbing water. (author)

  19. Strong resistance of Arabidopsis thaliana and Raphanus sativus seeds for ionizing radiation as studied by ESR, ENDOR, ESE spectroscopy and germination measurement: Effect of long-lived and super-long-lived radicals

    Kumagai, Jun; Katoh, Hiromi; Kumada, Takayuki; Tanaka, Atsushi; Tano, Shigemitsu; Miyazaki, Tetsuo

    2000-01-01

    Resistance of seeds for ionizing radiation effects on Arabidopsis thaliana and Raphanus sativus seeds were investigated by ESR, ENDOR, ESE spectroscopy and germination measurement. Two types of free radicals, such as long-lived (LL) and super-long-lived (SL) radicals, were produced by the γ-irradiation in the seeds. More than 90% of the 1 kGy-irradiated-seeds can germinate probably by decreasing the LL radicals by absorbing water. 10 kGy-irradiated-seeds cannot germinate at all probably due to the existence of significant amounts of the SL radicals even after absorbing water.

  20. Pulse on Pulse

    Schmidt, Ulrik; Carlson, Merete

    2012-01-01

    of the visitor’s beating heart to the blink of a fragile light bulb, thereby transforming each light bulb into a register of individual life. But at the same time the blinking light bulbs together produce a chaotically flickering light environment composed by various layers of repetitive rhythms, a vibrant...... and pulsating ‘room’. Hence, the visitors in Pulse Room are invited into a complex scenario that continuously oscillates between various aspects of signification (the light bulbs representing individual lives; the pulse itself as the symbolic ‘rhythm of life’) and instants of pure material processuality...... (flickering light bulbs; polyrhythmic layers). Taking our point of departure in a discussion of Gilles Deleuze’s concepts of modulation and signaletic material in relation to electronic media, we examine how the complex orchestration of pulsation between signification and material modulation produces...

  1. Pulse Voltammetry.

    Osteryoung, Janet

    1983-01-01

    Discusses the nature of pulse voltammetry, indicating that its widespread use arises from good sensitivity and detection limits and from ease of application and low cost. Provides analytical and mechanistic applications of the procedure. (JN)

  2. A 140 GHz pulsed EPR/212 MHz NMR spectrometer for DNP studies

    Smith, Albert A.; Corzilius, Björn; Bryant, Jeffrey A.; DeRocher, Ronald; Woskov, Paul P.; Temkin, Richard J.; Griffin, Robert G.

    2012-10-01

    We described a versatile spectrometer designed for the study of dynamic nuclear polarization (DNP) at low temperatures and high fields. The instrument functions both as an NMR spectrometer operating at 212 MHz (1H frequency) with DNP capabilities, and as a pulsed-EPR operating at 140 GHz. A coiled TE011 resonator acts as both an NMR coil and microwave resonator, and a double balanced (1H, 13C) radio frequency circuit greatly stabilizes the NMR performance. A new 140 GHz microwave bridge has also been developed, which utilizes a four-phase network and ELDOR channel at 8.75 GHz, that is then multiplied and mixed to obtain 140 GHz microwave pulses with an output power of 120 mW. Nutation frequencies obtained are as follows: 6 MHz on S = 1/2 electron spins, 100 kHz on 1H, and 50 kHz on 13C. We demonstrate basic EPR, ELDOR, ENDOR, and DNP experiments here. Our solid effect DNP results demonstrate an enhancement of 144 and sensitivity gain of 310 using OX063 trityl at 80 K and an enhancement of 157 and maximum sensitivity gain of 234 using Gd-DOTA at 20 K, which is significantly better performance than previously reported at high fields (⩾3 T).

  3. Pulse plating

    Hansal, Wolfgang E G; Green, Todd; Leisner, Peter; Reichenbach, Andreas

    2012-01-01

    The electrodeposition of metals using pulsed current has achieved practical importance in recent years. Although it has long been known that changes in potential, with or without polarity reversal, can significantly affect the deposition process, the practical application of this has been slow to be adopted. This can largely be explained in terms of the complex relationship between the current regime and its effect on the electrodeposition process. In order to harness these effects, an understanding of the anodic and cathodic electrochemical processes is necessary, together with the effects of polarity reversal and the rate of such reversals. In this new monograph, the basics of metal electrodeposition from solution are laid out in great detail in seven distinct chapters. With this knowledge, the reader is able to predict how a given pulse train profile can be adopted to achieve a desired outcome. Equally important is the choice of a suitable rectifier and the ancillary control circuits to enable pulse platin...

  4. Pulse radiolysis

    This supplement to two bibliographies published in 1970 and 1972 lists 734 references to the literature of pulse radiolysis, arranged under eight broad subject headings. The references were compiled by searching Biological Abstracts, Chemical Abstracts, Nuclear Science Abstracts and the Weekly List of Papers in Radiation Chemistry issued by the Radiation Chemistry Data Center of Notre Dame University. Full bibliographic data is given for papers published in the period 1971 to 1974. A personal author index listing more than 600 authors and a similar number of co-authors is included

  5. Pulse pile-up. I: Short pulses

    The search for rare large pulses against an intense background of smaller ones involves consideration of pulse pile-up. Approximate methods are presented, based on ruin theory, by which the probability of such pile-up may be estimated for pulses of arbitrary form and of arbitrary pulse-height distribution. These methods are checked against cases for which exact solutions are available. The present paper is concerned chiefly with short pulses of finite total duration. (Author) (5 refs., 24 figs.)

  6. Excimer Laser Pulse Compress With Pulse Feedback

    2008-01-01

    <正>To attain a shorter laser pulse, a compressing technique called pulse feedback was developed from the saturation gain switch applied to the amplification in a discharge pumping excimer laser cavity. It can

  7. Towards attosecond XUV pulses

    We are constructing a system for attosecond pulse generation via high-order harmonics generation in noble gases. To obtain a single attosecond pulse rather than a pulse train, we employ the regime of a few-cycle-pulse-driven harmonics generation. To achieve it, we are developing an external pulse compressor down to 7 - 10 fs using a gas-filled hollow fiber followed by chirped mirrors. We also proposed the method of high-energy attosecond pulse generation using high-order harmonics generated during the interaction of a relativistic-irradiance laser pulse with a thin foil. (author)

  8. Exploring intense attosecond pulses

    Charalambidis, D.; Tzallas, P.; Benis, E. P.; Skantzakis, E.; Maravelias, G.; Nikolopoulos, L. A. A.; Peralta Conde, A.; Tsakiris, G. D.

    2008-02-01

    After introducing the importance of non-linear processes in the extreme-ultra-violet (XUV) spectral regime to the attosecond (asec) pulse metrology and time domain applications, we present two successfully implemented techniques with excellent prospects in generating intense asec pulse trains and isolated asec pulses, respectively. For the generation of pulse trains two-color harmonic generation is exploited. The interferometric polarization gating technique appropriate for the generation of intense isolated asec pulses is discussed and compared to other relevant approaches.

  9. Inductive Pulse Generation

    Lindblom, Adam

    2006-01-01

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

  10. Generation of multi-hundred petawatt pulses by resonant Raman amplification in plasma

    Wu, Zhaohui; Zuo, Yanlei; Su, Jingqin; Liu, Lanqin; Zhang, Zhimeng; Li, Zhilin; Jiao, Zhihong; Wei, Xiaofeng

    2015-03-01

    Backward Raman amplification (BRA) in plasma has been proposed to produce overcritical high-power laser pulses. In this paper, an application based on CPA and BRA is promoted to generate multi-hundred petawatt laser pulses. The compression of short-wavelength (around 351 nm) and picosecond pulses has been proposed for high output intensity and short plasma length. This principle was employed in an application and a scheme is demonstrated using a full-kinetic particle-in-cell (PIC) code. The PIC code is also used to optimize key parameters in the resonant interaction. According to the simulated result using optimized parameters, the output seed fluence is amplified to 6.5 kJ/cm2 and the full-width at half-maximum duration is compressed to 13 fs, showing an energy transfer over 60%. Extending the result to the multidimensional case, a total energy of 3.9 kJ and a laser power of 300 PW are achievable, in a 0.6 cm2 interaction spot. This result is helpful for the improvement of high-energy density physics.

  11. Radial pulse (image)

    ... heart. The arteries are the vessels with the "pulse", a rhythmic pushing of the blood in the ... a refilling of the heart chamber. To determine heart rate, one feels the beats at a pulse point ...

  12. Wrist pulse (image)

    To measure the pulse at the wrist, place the index and middle finger over the underside of the opposite wrist, below the base ... firmly with flat fingers until you feel the pulse in the radial artery.

  13. Divided-Pulse Lasers

    Lamb, Erin S.; Wright, Logan G.; Wise, Frank W.

    2014-01-01

    We demonstrate the use of coherent division and recombination of the pulse within an ultrafast laser cavity to manage the nonlinear phase accumulation and scale the output pulse energy. We implement the divided-pulse technique in an ytterbium-doped fiber laser and achieve 16-times scaling of the pulse energy, to generate 6 nJ and 1.4 ps solitons in single mode fiber. Potential extensions of this concept are discussed.

  14. Pulse-Width Jitter Measurement for Laser Diode Pulses

    TANG Jun-Hua; WANG Yun-Cai

    2006-01-01

    @@ Theoretical analysis and experimental measurement of pulse-width jitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is deduced.

  15. Pulsed laser machining apparatus

    Apparatus and method for directing a controlled number of laser pulses onto a work piece to be machined. More specifically, the laser machining apparatus includes an excitable laser and an excitation lamp for continuously exciting the laser to emit a sequence of laser pulses. The application of the laser pulses to the work piece is controlled by an inner-cavity shutter that is opened to permit a precise number of pulses to be directed onto the work piece. The frequency (REP RATE) and pulse width of the laser pulses are controlled by the excitation lamp and, in turn, are set to create a progressive weld of significant depth and structural integrity. In particular there is provided control means for counting the number of laser pulses applied to a machining site of the work piece, whereby a known controllable quantity of energy is imparted to each site. To this end, the counting of the laser pulses begins after the completion of a laser pulse, whereby the actuation of the inner-cavity shutter is not synchronized to the computer but rather to the laser emission so that only whole laser pulses will be applied to the site

  16. High voltage pulse conditioning

    Springfield, Ray M.; Wheat, Jr., Robert M.

    1990-01-01

    Apparatus for conditioning high voltage pulses from particle accelerators in order to shorten the rise times of the pulses. Flashover switches in the cathode stalk of the transmission line hold off conduction for a determinable period of time, reflecting the early portion of the pulses. Diodes upstream of the switches divert energy into the magnetic and electrostatic storage of the capacitance and inductance inherent to the transmission line until the switches close.

  17. Pulsed Power Forming

    Gafri, O.; Izhar, A.; Livshitz, Y.; Shribman, V.

    2004-01-01

    R&D and application work in the sphere of Pulsed Power Forming (PPF) is well known and has been documented since the 1960's, along with its advantages. Pulsed Power Forming applications, which have been developed at Pulsar Ltd over the last decade, are described in this paper. Special equipment and tools for forming have been designed, developed, and manufactured, utilising pulsed magnetic fields. Theoretical and experimental research has been carried out to determine the magnetic field distr...

  18. Nonlinear pulse compression

    Grün, Alexander

    2014-01-01

    In this thesis I investigate two methods for generating ultrashort laser pulses in spectral regions which are ordinarily difficult to achieve by the existing techniques. These pulses are specially attractive in the study of ultrafast (few femtosecond) atomic and molecular dynamics. The first involves Optical Parametric Amplification (OPA) mediated by four-wave-mixing in gas and supports the generation of ultrashort pulses in the Near-InfraRed (NIR) to the Mid-InfraRed (MIR) spectral regio...

  19. Opportunities in pulse combustion

    Brenchley, D. L.; Bomelburg, H. J.

    1985-10-01

    In most pulse combustors, the combustion occurs near the closed end of a tube where inlet valves operate in phase with the pressure amplitude variations. Thus, within the combustion zone, both the temperature and the pressure oscillate around a mean value. However, the development of practical applications of pulse combustion has been hampered because effective design requires the right combination of the combustor's dimensions, valve characteristics, fuel/oxidizer combination, and flow pattern. Pulse combustion has several additional advantages for energy conversion efficiency, including high combustion and thermal efficiency, high combustion intensity, and high convective heat transfer rates. Also, pulse combustion can be self-aspirating, generating a pressure boost without using a blower. This allows the use of a compact heat exchanger that may include a condensing section and may obviate the need for a chimney. In the last decade, these features have revived interest in pulse combustion research and development, which has resulted in the development of a pulse combustion air heater by Lennox, and a pulse combustion hydronic unit by Hydrotherm, Inc. To appraise this potential for energy savings, a systematic study was conducted of the many past and present attempts to use pulse combustion for practical purposes. The authors recommended areas where pulse combustion technology could possibly be applied in the future and identified areas in which additional R and D would be necessary. Many of the results of the study project derived from a special workshop on pulse combustion. This document highlights the main points of the study report, with particular emphasis on pulse combustion application in chemical engineering.

  20. Pulse pile-up effects

    The energy spectrum containing the effects of all orders of pulse pileup is predicted for an idealized x-ray pulse-height-analysis system measuring randomly occurring events. Two simplifying assumptions used are first a fixed pulse resolution time and second that the measured energy of piled-up pulses is the algebraic sum of the energy associated with each pulse

  1. Composite Pulse Tube

    Martin, Jerry L.; Cloyd, Jason H.

    2007-01-01

    A modification of the design of the pulse tube in a pulse-tube cryocooler reduces axial thermal conductance while preserving radial thermal conductance. It is desirable to minimize axial thermal conductance in the pulse-tube wall to minimize leakage of heat between the warm and cold ends of the pulse tube. At the same time, it is desirable to maximize radial thermal conductance at the cold end of the pulse tube to ensure adequate thermal contact between (1) a heat exchanger in the form of a stack of copper screens inside the pulse tube at the cold end and (2) the remainder of the cold tip, which is the object to which the heat load is applied and from which heat must be removed. The modified design yields a low-heat-leak pulse tube that can be easily integrated with a cold tip. A typical pulse tube of prior design is either a thin-walled metal tube or a metal tube with a nonmetallic lining. It is desirable that the outer surface of a pulse tube be cylindrical (in contradistinction to tapered) to simplify the design of a regenerator that is also part of the cryocooler. Under some conditions, it is desirable to taper the inner surface of the pulse tube to reduce acoustic streaming. The combination of a cylindrical outer surface and a tapered inner surface can lead to unacceptably large axial conduction if the pulse tube is made entirely of metal. Making the pulse-tube wall of a nonmetallic, lowthermal- conductivity material would not solve the problem because the wall would not afford the needed thermal contact for the stack of screens in the cold end. The modified design calls for fabricating the pulse tube in two parts: a longer, nonmetallic part that is tapered on the inside and cylindrical on the outside and a shorter, metallic part that is cylindrical on both the inside and the outside. The nonmetallic part can be made from G-10 fiberglass-reinforced epoxy or other low-thermal-conductivity, cryogenically compatible material. The metallic part must have high

  2. Pulse Distortion in Saturated Fiber Optical Parametric Chirped Pulse Amplification

    Lali-Dastjerdi, Zohreh; Da Ros, Francesco; Rottwitt, Karsten;

    2012-01-01

    Fiber optical parametric chirped pulse amplification is experimentally compared for different chirped pulses in the picosecond regime. The amplified chirped pulses show distortion appearing as pedestals after recompression when the amplifier is operated in saturation.......Fiber optical parametric chirped pulse amplification is experimentally compared for different chirped pulses in the picosecond regime. The amplified chirped pulses show distortion appearing as pedestals after recompression when the amplifier is operated in saturation....

  3. Thermal pulse energy harvesting

    This paper presents a new method to enhance thermal energy harvesting with pulsed heat transfer. By creating a phase shift between the hot and cold sides of an energy harvester, periodically pulsed heat flow can allow an available temperature gradient to be concentrated over a heat engine during each thermal pulse, rather than divided between the heat engine and a heat sink. This effect allows the energy harvester to work at maximum power and efficiency despite an otherwise unfavorable heat engine–heat sink thermal resistance ratio. In this paper, the analysis of a generalized energy harvester model and experiments with a mechanical thermal switch demonstrate how the pulse mode can improve the efficiency of a system with equal engine and heat sink thermal resistances by over 80%, although at reduced total power. At a 1:2 engine–sink resistance ratio, the improvement can simultaneously exceed 60% in power and 15% in efficiency. The thermal pulse strategy promises to enhance the efficiency and power density of a variety of systems that convert thermal energy, from waste heat harvesters to the radioisotope power systems on many spacecraft. - Highlights: • A thermal pulse operating mode can increase the maximum power of many thermal energy harvesting systems. • Two modes of pulsed heat transfer were modeled and compared to proof-of-concept experiments. • At a 1:2 heat engine–heat sink thermal resistance ratio, the enhancement exceeds 60% in power and 15% in efficiency

  4. An investigation into the initial degradation steps of four major dye chromophores: Study of their one-electron oxidation and reduction by EPR, ENDOR, cyclic voltanunetry, and theoretical calculations

    Stanoeva, T.; Neshchadin, D.; Gescheidt, G.; Ludvík, Jiří; Lajoie, B.; Batchelor, N.

    2005-01-01

    Roč. 109, č. 49 (2005), s. 11103-11109. ISSN 1089-5639 R&D Projects: GA AV ČR IAA4040304 Institutional research plan: CEZ:AV0Z40400503 Keywords : visible light * azo dye * photocatalytic degradation * pulse radiolysis Subject RIV: CG - Electrochemistry Impact factor: 2.898, year: 2005

  5. Pulse joining cartridges

    Golovashchenko, Sergey Fedorovich; Bonnen, John Joseph Francis

    2016-08-23

    A pulsed joining tool includes a tool body that defines a cavity that receives an inner tubular member and an outer tubular member and a pulse joining cartridge. The tubular members are nested together with the cartridge being disposed around the outer tubular member. The cartridge includes a conductor, such as a wire or foil, that extends around the outer tubular member and is insulated to separate a supply segment from a return segment. A source of stored electrical energy is discharged through the conductor to join the tubular members with an electromagnetic force pulse.

  6. DogPulse

    Skovgaard, Christoffer; Thomsen, Josephine Raun; Verdezoto, Nervo;

    2015-01-01

    This paper presents DogPulse, an ambient awareness system to support the coordination of dog walking among family members at home. DogPulse augments a dog collar and leash set to activate an ambient shape-changing lamp and visualize the last time the dog was taken for a walk. The lamp gradually...... changes its form and pulsates its lights in order to keep the family members aware of the dog walking activity. We report the iterative prototyping of DogPulse, its implementation and its preliminary evaluation. Based on our initial findings, we present the limitations and lessons learned as well as...

  7. Whispering Gallery Pulse Compressor

    A barrel-like cavity resonant at a whispering gallery mode is known as capable to provide a SLED-like rf pulse compression. To enhance the power handling capacity of the compressor, we propose to use a coupler based on a wave tunneling through a continuous slot. A modeling low power 11.4 GHz experiment proved to be consistent with theory. A preliminary technical design for an evacuated high-power compressor has also been developed. According to a theory, a twin-cavity version of the device can efficiently compress microwave pulses produced with sources of limited bandwidth, in particular frequency-chirped pulses

  8. Efficient Pulsed Quadrupole

    Petzenhauser, I.; Spiller, P.; Tenholt, C.

    2016-01-01

    In order to raise the focusing gradient in case of bunched beam lines, a pulsed quadrupole was designed. The transfer channels between synchrotrons as well as the final focusing for the target line are possible applications. The quadrupole is running in a pulsed mode, which means an immense saving of energy by avoiding standby operation. Still the high gradients demand high currents. Hence a circuit had to be developed which is able to recover a significant amount of the pulsing energy for following shots. The basic design of the electrical circuit of the quadrupole is introduced. Furthermore more energy efficient circuits are presented and the limits of adaptability are considered.

  9. Intense pulsed neutron sources

    Kustom, R.L.

    1981-01-01

    Accelerator requirements for pulsed spallation neutron sources are stated. Brief descriptions of the Argonne IPNS-I, the Japanese KENS, Los Alamos Scientific Laboratory WNR/PSR, the Rutherford Laboratory SNS, and the West German SNQ facilities are presented.

  10. Pulse polarography - special application

    The calculation of the current on a plane electrode in particular conditions is presented briefly, the first part of the report then consists of a theoretical and methodological presentation of pulse polarography. The calculation of the current in pulse polarography is given for different modes of measurement and for redox systems of variable reversibility. Various extensions are proposed with a view to extending the field of application of the method. The second part presents two particular applications. One application is to analytical chemistry: organometallic complexes applied to the pulse polarographic analysis; the other application is to electrochemical kinetics using integral pulse polarography. This research has enabled us to determine, in the first case, elements present in minute traces, and in the second case the kinetic parameters of an electrochemical reaction which is too fast to be analyzed by conventional polarography. (author)

  11. Pulse holographic measurement techniques

    With the development of laser, remote inspection techniques using laser have been growing on. The inspection and measurement techniques by pulse holography are well-established technique for precise measurement, and widely used in various fields of industry now. In nuclear industry, this technology is practically used because holographic inspection is remote, noncontact, and precise measurement technique. In relation to remote inspection technology in nuclear industry, state-of-the art of pulse HNDT (Holographic non-destructive testing) and holographic measurement techniques are examined. First of all, the fundamental principles as well as practical problems for applications are briefly described. The fields of pulse holography have been divided into the HNDT, flow visualization and distribution study, and other application techniques. Additionally holographic particle study, bubble chamber holography, and applications to other visualization techniques are described. Lastly, the current status for the researches and applications of pulse holography to nuclear industry which are carried out actively in Europe and USA, is described. (Author)

  12. A directive pulse antenna

    Titov, A.N.; Titov, A. A.

    2003-01-01

    Using quite general concepts as guidance in the design of an antenna for short pulse transmission and reception, a new type of horn-antenna has been devised. A certain variety of experimental data obtained by the antenna are presented.

  13. Pulse measurement apparatus and method

    Marciante, John R.; Donaldson, William R.; Roides, Richard G.

    2011-10-25

    An embodiment of the invention is directed to a pulse measuring system that measures a characteristic of an input pulse under test, particularly the pulse shape of a single-shot, nano-second duration, high shape-contrast optical or electrical pulse. An exemplary system includes a multi-stage, passive pulse replicator, wherein each successive stage introduces a fixed time delay to the input pulse under test, a repetitively-gated electronic sampling apparatus that acquires the pulse train including an entire waveform of each replica pulse, a processor that temporally aligns the replicated pulses, and an averager that temporally averages the replicated pulses to generate the pulse shape of the pulse under test. An embodiment of the invention is directed to a method for measuring an optical or an electrical pulse shape. The method includes the steps of passively replicating the pulse under test with a known time delay, temporally stacking the pulses, and temporally averaging the stacked pulses. An embodiment of the invention is directed to a method for increasing the dynamic range of a pulse measurement by a repetitively-gated electronic sampling device having a rated dynamic range capability, beyond the rated dynamic range of the sampling device; e.g., enhancing the dynamic range of an oscilloscope. The embodied technique can improve the SNR from about 300:1 to 1000:1. A dynamic range enhancement of four to seven bits may be achieved.

  14. Pulsed spallation Neutron Sources

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

  15. Pulsed spallation neutron sources

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

  16. Ultrashort pulse induced nanogratings

    Nolte Stefan

    2013-11-01

    Full Text Available When intense femtosecond laser pulses are focused into a glass substrate, self-organized periodic nanostructures, so-called nanogratings, are generated in a certain parameter regime. To clarify the ultimate structure of the nanogratings we employed focused ion beam (FIB milling and small angle X-ray scattering (SAXS. The results considerably show that voids are the primary constituents and their number increases with ongoing exposure to laser pulses. Potential applications will be highlighted.

  17. Magnetic Pulse Welding Technology

    Ahmad K. Jassim

    2011-01-01

    In this paper, the benefits of using Magnetic Pulse machine which is belong to Non-conventional machine instead of conventional machine. Magnetic Pulse Technology is used for joining dissimilar metals, and for forming and cutting metals. It is a non contact technique. Magnetic field is used to generate impact magnetic pressure for welding and forming the work piece by converted the electrical energy to mechanical energy. It is enable us to design previously not possible by weld...

  18. Pulsed spallation Neutron Sources

    Carpenter, J.M. [Argonne National Lab., IL (United States)

    1994-12-31

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

  19. Pulse Onset Detection using Neighbor Pulse-Based Signal Enhancement

    Xu, Peng; Bergsneider, Marvin; Hu, Xiao

    2008-01-01

    Detecting onsets of cardiovascular pulse wave signals is an important prerequisite for successfully conducting various analysis tasks involving the concept of pulse wave velocity. However, pulse onsets are frequently influenced by inherent noise and artifacts in signals continuously acquired in a clinical environment. The present work proposed and validated a neighbor pulse-based signal enhancement algorithm for reducing error in the detected pulse onset locations from noise-contaminated puls...

  20. Cosmic ray intensity pulses

    Pulse variations in the galactic cosmic ray intensity, extending over intervals of several hours, have often been observed during cosmic ray storms as well as during other periods. On some occasions, these pulses appear in the data recorded at polar stations during epochs characterized by enhanced diurnal anisotropy at low latitudes. The short-term intensity increase at polar stations cannot be ascribed solely to the azimuthal anisotropy, and it is demonstrated that the cosmic ray transport during a pulse displays both azimuthal and north-south anisotropies. Furthermore, it is found that the magnetude of the pulse height recorded by a station i is proportional to /sup j/u where μ/sub i/=cos theta, and theta/sub i/ is the angular separation between the mean asymptotic direction of viewing of station i and the direction of anisotropy in three dimentional space. The relationship between pulse modulations and transient disturbances in the interplanetary magnetic field, and especially their location, remain to be investigated

  1. Herophilus on pulse

    Afonasin, Eugene

    2015-01-01

    Full Text Available The first detailed study of the pulse (sphygmology is associated in antiquity with Herophilus (the end of the 4th century BCE, an Alexandrian physician, renowned for his anatomical discoveries. The scholars also attribute to him a discovery of a portable and adjustable water-clock, used for measuring ‘natural’ and ‘unnatural’ pulse and, accordingly, temperature of the patient. In the article we translate the principal ancient evidences and comment upon them. We study both the practical aspects of ancient sphygmology and the theoretical speculations associated with it. Ancient theory of proportion and musical harmony allowed to build a classification of the pulses, but the medical experience did not fit well in the Procrustean bed of this rather simple theory.

  2. Discharge pulse phenomenology

    Frederickson, A. R.

    1985-01-01

    A model was developed which places radiation induced discharge pulse results into a unified conceptual framework. Only two phenomena are required to interpret all space and laboratory results: (1) radiation produces large electrostatic fields inside insulators via the trapping of a net space charge density; and (2) the electrostatic fields initiate discharge streamer plasmas similar to those investigated in high voltage electrical insulation materials; these streamer plasmas generate the pulsing phenomena. The apparent variability and diversity of results seen is an inherent feature of the plasma streamer mechanism acting in the electric fields which is created by irradiation of the dielectrics. The implications of the model are extensive and lead to constraints over what can be done about spacecraft pulsing.

  3. Pulse Doppler radar

    Alabaster, Clive

    2012-01-01

    This book is a practitioner's guide to all aspects of pulse Doppler radar. It concentrates on airborne military radar systems since they are the most used, most complex, and most interesting of the pulse Doppler radars; however, ground-based and non-military systems are also included. It covers the fundamental science, signal processing, hardware issues, systems design and case studies of typical systems. It will be a useful resource for engineers of all types (hardware, software and systems), academics, post-graduate students, scientists in radar and radar electronic warfare sectors and milit

  4. Millimicrosecond pulse techniques

    Lewis, Ian A D

    1959-01-01

    Millimicrosecond Pulse Techniques, Second Edition focuses on millimicrosecond pulse techniques and the development of devices of large bandwidth, extending down to comparatively low frequencies (1 Mc/s). Emphasis is on basic circuit elements and pieces of equipment of universal application. Specific applications, mostly in the field of nuclear physics instrumentation, are considered. This book consists of eight chapters and opens with an introduction to some of the terminology employed by circuit engineers as well as theoretical concepts, including the laws of circuit analysis, Fourier analysi

  5. Modeling magnetic pulse compressors

    In this paper, the author considers the problem of modeling the dynamic performance of high-average-power, high repetition-rate magnetic pulse compressors. The author is particularly concerned with developing system models suitable for studying output pulse stability in high repetition rate applications. To this end, the author presents a magnetic switch model suitable for system studies and discusses a modeling tool being developed to perform these studies. The author concludes with some preliminary results of efforts to simulate the MAG1D compressor performance

  6. SNMR pulse sequence phase cycling

    Walsh, David O; Grunewald, Elliot D

    2013-11-12

    Technologies applicable to SNMR pulse sequence phase cycling are disclosed, including SNMR acquisition apparatus and methods, SNMR processing apparatus and methods, and combinations thereof. SNMR acquisition may include transmitting two or more SNMR pulse sequences and applying a phase shift to a pulse in at least one of the pulse sequences, according to any of a variety cycling techniques. SNMR processing may include combining SNMR from a plurality of pulse sequences comprising pulses of different phases, so that desired signals are preserved and indesired signals are canceled.

  7. Pulse distortion in single-mode fibers. 3: Chirped pulses.

    Marcuse, D

    1981-10-15

    The theory of pulse distortion in single-mode fibers is extended to include laser sources that suffer a linear wavelength sweep (chirp) during the duration of the pulse. The transmitted pulse is expressed as a Fourier integral whose spectral function is given by an analytical expression in closed form. The rms width of the transmitted pulse is also expressed in closed form. Numerical examples illustrate the influence of the chirp on the shape and rms width of the pulse. A somewhat paradoxical situation exists. A given input pulse can be made arbitrarily short by a sufficiently large amount of chirping, and, after a given fiber length, this chirped pulse returns to its original width. But at this particular distance an unchirped pulse would be only [equiation] times longer. Thus chirping can improve the rate of data transmission by only 40%. PMID:20372221

  8. Pulsed inductive HF laser

    Razhev, A. M.; Churkin, D. S.; Kargapol'tsev, E. S.; Demchuk, S. V.

    2016-03-01

    We report the results of experimentally investigated dependences of temporal, spectral and spatial characteristics of an inductive HF-laser generation on the pump conditions. Gas mixtures H2 – F2(NF3 or SF66) and He(Ne) – H2 – F2(NF3 or SF6) were used as active media. The FWHM pulse duration reached 0.42 μs. This value corresponded to a pulsed power of 45 kW. For the first time, the emission spectrum of an inductive HF laser was investigated, which consisted of seven groups of bands with centres around the wavelengths of 2732, 2736, 2739, 2835, 2837, 2893 and 2913 nm. The cross section profile of the laser beam was a ring with a diameter of about 20 mm and width of about 5 mm. Parameters of laser operation in the repetitively pulsed regime were sufficiently stable. The amplitude instability of light pulses was no greater than 5% – 6%.

  9. Pulsed electric fields

    The concept of pulsed electric fields (PEF) was first proposed in 1967 to change the behavior or microorganisms. The electric field phenomenon was identified as membrane rupture theory in the 1980s. Increasing the membrane permeability led to the application of PEF assisted extraction of cellular co...

  10. Lectures on pulsed NMR

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 32 refs., 56 figs

  11. Lectures on pulsed NMR

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 55 figs

  12. Analog pulse processor

    Wessendorf, Kurt O.; Kemper, Dale A.

    2003-06-03

    A very low power analog pulse processing system implemented as an ASIC useful for processing signals from radiation detectors, among other things. The system incorporates the functions of a charge sensitive amplifier, a shaping amplifier, a peak sample and hold circuit, and, optionally, an analog to digital converter and associated drivers.

  13. Interferometry in pulsed fields

    Döbrich, Babette; Gies, Holger

    2009-01-01

    We discuss the particle-physics discovery potential of ground-based gravitational-wave interferometers. With the use of pulsed magnetic fields, current and future gravitational-wave interferometers could not only be utilized to observe phenomena of strong-field QED, but they could also be applied to sweep the parameter space of particles of the hidden sector.

  14. Propagation of cold pulses and heat pulses in ASDEX Upgrade

    Experiments on electron heat transport were performed in the tokamak ASDEX Upgrade, mainly in ohmically heated plasmas, applying either edge cooling by impurity injection or edge heat pulses with ECH. Repetitive pulses within one plasma discharge were made allowing Fourier transformation of the temperature perturbation. This yields a good signal to noise ratio up to high harmonics and allows a detailed investigation of the pulse propagation. For densities lower than 1.8x1019m-3, an increase of the central electron temperature was found as the response to the edge cooling via impurity injection similar to observations made in other tokamaks. The inversion does not appear instantaneously, but with a time delay roughly compatible with diffusion. Modeling of the propagation of the cold pulses in the framework of the IFS-PPPL model yields qualitative agreement. However the predicted increase of the ion temperature is not observed experimentally on the fast time scale. The response to ECH heat pulses is not perfectly symmetrical to cold pulse experiments, but the similarities suggest a common underlying physical mechanism. No inversion of the heat pulse is found, instead the initial pulse from the edge is associated with a second, much slower heat pulse in the centre which is similar (and not symmetrical) to that of the cold pulses. It is found that the central increase is related to the arrival of the pulse close to the inversion radius and not to the initial pulse. (author)

  15. Wide spectrum microwave pulse measurement

    King, R.J.

    1986-01-01

    Various techniques are postulated as diagnostics for wide band microwave pulses. The diagnostics include determinations of both the instantaneous amplitude and the frequency content of one-shot pulses. 6 refs., 11 figs. (WRF)

  16. Wide spectrum microwave pulse measurement

    Various techniques are postulated as diagnostics for wide band microwave pulses. The diagnostics include determinations of both the instantaneous amplitude and the frequency content of one-shot pulses. 6 refs., 11 figs

  17. Recent advances in pulse oximetry

    Cannesson, Maxime; Talke, Pekka

    2009-01-01

    Conventional pulse oximetry uses two wavelengths of light (red and infrared) transmitted through a finger and a photodetector to analyze arterial hemoglobin oxygen saturation and pulse rate. Recent advances in pulse oximetry include: extended analysis of the photo plethysmographic waveform; use of multiple wavelengths of light to quantify methemoglobin, carboxyhemoglobin and total hemoglobin content in blood; and use of electronic processes to improve pulse oximeter signal processing during c...

  18. Sequentially pulsed traveling wave accelerator

    Caporaso, George J.; Nelson, Scott D.; Poole, Brian R.

    2009-08-18

    A sequentially pulsed traveling wave compact accelerator having two or more pulse forming lines each with a switch for producing a short acceleration pulse along a short length of a beam tube, and a trigger mechanism for sequentially triggering the switches so that a traveling axial electric field is produced along the beam tube in synchronism with an axially traversing pulsed beam of charged particles to serially impart energy to the particle beam.

  19. Bacterial inactivation using pulsed light

    Elmnasser, Noura; Ritz, Magali; Leroi, Francoise; Orange, Nicole; Bakhrouf, Amina; Federighi, Michel

    2007-01-01

    Pulsed light is a new method intended for the decontamination of food surfaces using short, high frequency pulses of an intense broad spectrum. The effects of broad spectrum pulsed light on the survival of Listeria monocytogenes Scott A, Listeria monocytogenes CNL, Pseudomonas fluorescens MF37 and Photobacterium phosphoreum SF680 populations on agar and in a liquid medium were investigated during this study. The sterilisation system generated 1.5 J cm(-2) per pulse with eight lamps for 300 mu...

  20. Design of a pulse stacker

    A pulse stacker for the 100p sec short laser pulse produced by the Nd-glass laser VULCAN has been designed which has 150p sec between reflections. It was found that three or four plates (i.e. 6-8 surfaces) are needed to generate the approximately equal to 1 nsec pulse required. (U.K.)

  1. Pulsed power for EMP simulators

    Simulation of nuclear weapons effects has been the main motivation for pulse power development in the US in the last decade. EMP simulation has been responsible for a major class of pulse power systems. A general survey of pulse power techniques is given, focusing of those particularly applicable for EMP simulation. This is followed by brief descriptions of several representative simulators

  2. Short pulse neutron generator

    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. Noisy homoclinic pulse dynamics

    Eaves, T. S.; Balmforth, Neil J.

    2016-04-01

    The effect of stochastic perturbations on nearly homoclinic pulse trains is considered for three model systems: a Duffing oscillator, the Lorenz-like Shimizu-Morioka model, and a co-dimension-three normal form. Using the Duffing model as an example, it is demonstrated that the main effect of noise does not originate from the neighbourhood of the fixed point, as is commonly assumed, but due to the perturbation of the trajectory outside that region. Singular perturbation theory is used to quantify this noise effect and is applied to construct maps of pulse spacing for the Shimizu-Morioka and normal form models. The dynamics of these stochastic maps is then explored to examine how noise influences the sequence of bifurcations that take place adjacent to homoclinic connections in Lorenz-like and Shilnikov-type flows.

  4. Magnetic Pulse Welding Technology

    Ahmad K. Jassim

    2011-12-01

    Full Text Available In this paper, the benefits of using Magnetic Pulse machine which is belong to Non-conventional machine instead of conventional machine. Magnetic Pulse Technology is used for joining dissimilar metals, and for forming and cutting metals. It is a non contact technique. Magnetic field is used to generate impact magnetic pressure for welding and forming the work piece by converted the electrical energy to mechanical energy. It is enable us to design previously not possible by welding dissimilar materials and allowing to welds light and stronger materials together. It can be used to weld metallic with non metallic materials to created mechanical lock on ceramics, polymers, rubbers and composites. It is green process; there is no heat, no radiation, no gas, no smoke and sparks, therefore the emissions are negligible.

  5. Computationally intelligent pulsed photoacoustics

    In this paper, the application of computational intelligence in pulsed photoacoustics is discussed. Feedforward multilayer perception networks are applied for real-time simultaneous determination of the laser beam spatial profile and vibrational-to-translational relaxation time of the polyatomic molecules in gases. Networks are trained and tested with theoretical data adjusted for a given experimental set-up. Genetic optimization has been used for calculation of the same parameters, fitting the photoacoustic signals with a different number of generations. Observed benefits from the application of computational intelligence in pulsed photoacoustics and advantages over previously developed methods are discussed, such as real-time operation, high precision and the possibility of finding solutions in a wide range of parameters, similar to in experimental conditions. In addition, the applicability for practical uses, such as the real-time in situ measurements of atmospheric pollutants, along with possible further developments of obtained results, is argued. (paper)

  6. Pulsed fusion reactors

    This summer school specialized in examining specific fusion center systems. Papers on scientific feasibility are first presented: confinement of high-beta plasma, liners, plasma focus, compression and heating and the use of high power electron beams for thermonuclear reactors. As for technological feasibility, lectures were on the theta-pinch toroidal reactors, toroidal diffuse pinch, electrical engineering problems in pulsed magnetically confined reactors, neutral gas layer for heat removal, the conceptual design of a series of laser fusion power plants with ''Saturn'', implosion experiments and the problem of the targets, the high brightness lasers for plasma generation, and topping and bottoming cycles. Some problems common to pulsed reactors were examined: energy storage and transfer, thermomechanical and erosion effects in the first wall and blanket, the problems of tritium production, radiation damage and neutron activation in blankets, and the magnetic and inertial confinement

  7. Pulsed laser microtomograph

    Antonov, V. B.; Bonch-Bruevich, A. M.; Vasil'Ev, V. I.; Ionov, L. N.; Nikolaev, S. D.; Starobogatov, I. O.

    1994-12-01

    This paper describes a pulsed laser tomographic apparatus that has been implemented in practice and has a spatial resolution of 2-5 microns in the transverse direction and approximately 70 microns in the probe-radiation propagation direction. Experiments have been performed with model objects. Results have been obtained that confirm the possibility of early diagnosis of skin mycoses that cannot be diagnosed by existing methods.

  8. STUCTURE OF PULSED BED

    I. A. Bokun

    2014-01-01

    Full Text Available The structure of pulsed layer is proposed which can be suggested as a state of particulates that is blown by intermittent gas flow with speed which has the force to start material moving. Layer during one cycle is in a suspension, falling down and immobile state resulting in changes of particles arrangement as well as ways of gas flowing through layer. Moreover, it allows carrying out effective interphase heat exchange even adamant real granulation.The process of formation of impact flows is considered aw well as their influence on formation of air bubbles in pulsed layer. At startup of air blast the balance between the force of hydro-dynamic resistance is broken, on one side, and forces of gravity, particles inertia and their links with walls on the other side. The layer is transferred in the state of pulsed pseudo-fluidization, and presents gas-disperse mixture, inside of which impulse of pressure increasing is spreading to all sides as pressure waves (compression. These waves are the sources of impact flows’ formation, the force of which is two times more than during the stationary flow.The waves of pressure are divided into weak and strong ones depending on movement velocity within gas-disperse system. Weak waves are moving with a sound speed and strong ones in active phase of pulsed layer are moving over the speed of sound limit within gas-disperse system. The peculiarity of strong wave is that parameters of system (pressure, density and others are changing in discrete steps.The article describes the regime of layer’s falling down in the passive stage of cycle, which begins after finishing of gas impulse action. And suspension layer of moving up granular material is transferred in the state of falling resulting in change of the layer structure.

  9. Compact pulsed accelerator

    The formation of fast pulses from a current charged transmission line and opening switch is described. By employing a plasma focus as an opening switch and diode in the prototype device, a proton beam of peak energy 250 keV is produced. The time integrated energy spectrum of the beam is constructed from a Thomson spectrograph. Applications of this device as an inexpensive and portable charged particle accelerator are discussed. 7 refs., 5 figs., 1 tab

  10. Pulse Portraiture: Pulsar timing

    Pennucci, Timothy T.; Demorest, Paul B.; Ransom, Scott M.

    2016-06-01

    Pulse Portraiture is a wideband pulsar timing code written in python. It uses an extension of the FFTFIT algorithm (Taylor 1992) to simultaneously measure a phase (TOA) and dispersion measure (DM). The code includes a Gaussian-component-based portrait modeling routine. The code uses the python interface to the pulsar data analysis package PSRCHIVE (ascl:1105.014) and also requires the non-linear least-squares minimization package lmfit (ascl:1606.014).

  11. Highly integrated pulse processor

    A digital pulse processor for a multichannel solid-state detector has been designed, using highly integrated analog and digital signal processing circuits. The detector preamplifier output is digitized and a parametrizable synchro is elaborated by a dedicated chipset. The digitized signal is then processed by a finite impulse response filter chip (FIR) whose programming is discussed, after which a pile-up protected peak detector sorts it into a histogram. All parameters are digitally controlled. ((orig.))

  12. PULSE Pilot Certification Results

    Pamela Pape-Lindstrom

    2015-08-01

    Full Text Available The pilot certification process is an ambitious, nationwide endeavor designed to motivate important changes in life sciences education that are in line with the recommendations of the 2011 Vision and Change Report: A Call to Action (American Association for the Advancement of Science [AAAS], 2011.  It is the goal of the certification process to acknowledge departments that have progressed towards full implementation of the tenets of Vision and Change and to motivate departments that have not begun to adopt the recommendations to consider doing so.  More than 70 life science departments applied to be part of the pilot certification process, funded by a National Science Foundation grant, and eight were selected based on initial evidence of transformed and innovative educational practices.  The programs chosen represent a wide variety of schools, including two-year colleges, liberal-arts institutions, regional comprehensive colleges, research universities and minority serving institutions.  Outcomes from this pilot were released June 1, 2015 (www.pulsecommunity.org, with all eight programs being recognized as having progressed along a continuum of change.  Five levels of achievement were defined as PULSE Pilot Progression Levels.  Of the eight departments in the pilot, one achieved “PULSE Progression Level III: Accomplished”.  Six departments achieved “PULSE Progression Level II: Developing” and one pilot department achieved “PULSE Progression Level I: Beginning”.  All of the schools have made significant movement towards the recommendations of Vision and Change relative to a traditional life sciences curriculum.  Overall, the response from the eight pilot schools has been positive. 

  13. Pulsed Superconductivity Acceleration

    Liepe, M

    2000-01-01

    The design of the proposed linear collider TESLA is based on 9-cell 1.3 GHz superconducting niobium cavities, operated in pulsed mode. Within the framework of an international collaboration the TESLA Test Facility (TTF) has been set up at DESY, providing the infrastructure for cavity R&D towards higher gradients. More than 60 nine-cell cavities were tested, accelerating gradients as high as 30 MV/m were measured. In the second production of TTF-cavities the average gradient was measured to be 24.7 MV/m. Two modules, each containing eight resonators, are presently used in the TTF-linac. These cavities are operated in pulsed mode: 0.8 ms constant gradient with up to 10 Hz repetitions rate. We will focus on two aspects: Firstly, the cavity fabrication and treatment is discussed, allowing to reach high gradients. Latest results of single cell cavities will be shown, going beyond 40 MV/m. Secondly, the pulsed mode operation of superconducting cavities is reviewed. This includes Lorentz force detuning, mechanic...

  14. Pulse radiolysis of gases

    The pulse radiolysis equipment and technique are described and its relevance to atmospheric chemistry is discussed. Pulse radiolysis of a number of different chemical systems have been used to check the validity of the proposed mechanisms: 1) The hydrogen atom yield in the pulse radiolysis of H2 was measured by four independent calibration techniques, using reactions of H with O2, C1NO, and HI. The H atom yield was compared with O2 yields in pure O2 and in O2/SF6 mixtures which lead to a value G(H) = 17.6. The rate constants at room temperature of several reactions were determined. 2) OH radical reactions with tetraalkyllead at room temperature and with ethane, methane, and a series of C1- and F-substituted methanes at 300-400 K were studied. Arrhenius parameters, A and Esub(a), were determined for several reactions. The lifetime of Pb(CH3)4 and Pb(C2H5)4 in ambient air is estimated. CF2C12 was found to be a very efficient third body, M, in the reaction OH + OH + M arrow H2O2 + M. 3) In the H2S systems the HS extinction coefficient at 3242 AA was determined to 9.5 x 102 cm-1 mol-1. Four rate constants at room temperature were determined. (author)

  15. Petawatt pulsed-power accelerator

    Stygar, William A. (Albuquerque, NM); Cuneo, Michael E. (Albuquerque, NM); Headley, Daniel I. (Albuquerque, NM); Ives, Harry C. (Albuquerque, NM); Ives, legal representative; Berry Cottrell (Albuquerque, NM); Leeper, Ramon J. (Albuquerque, NM); Mazarakis, Michael G. (Albuquerque, NM); Olson, Craig L. (Albuquerque, NM); Porter, John L. (Sandia Park, NM); Wagoner; Tim C. (Albuquerque, NM)

    2010-03-16

    A petawatt pulsed-power accelerator can be driven by various types of electrical-pulse generators, including conventional Marx generators and linear-transformer drivers. The pulsed-power accelerator can be configured to drive an electrical load from one- or two-sides. Various types of loads can be driven; for example, the accelerator can be used to drive a high-current z-pinch load. When driven by slow-pulse generators (e.g., conventional Marx generators), the accelerator comprises an oil section comprising at least one pulse-generator level having a plurality of pulse generators; a water section comprising a pulse-forming circuit for each pulse generator and a level of monolithic triplate radial-transmission-line impedance transformers, that have variable impedance profiles, for each pulse-generator level; and a vacuum section comprising triplate magnetically insulated transmission lines that feed an electrical load. When driven by LTD generators or other fast-pulse generators, the need for the pulse-forming circuits in the water section can be eliminated.

  16. Band-selective radiofrequency pulses

    Geen, Helen; Freeman, Ray

    A theoretical treatment is given of the general problem of designing amplitude-modulated radiofrequency pulses that will excite a specified band of frequencies within a high-resolution NMR spectrum with uniform intensity and phase but with negligible excitation elsewhere. First a trial pulse envelope is defined in terms of a finite Fourier series and its frequency-domain profile calculated through the Bloch equations. The result is compared with the desired target profile to give a multidimensional error surface. The method of simulated annealing is then used to find the global minimum on this surface and the result refined by standard gradient-descent optimization. In this manner, a family of new shaped radio-frequency pulses, known as BURP ( band-selective, uniform response, pure-phase) pulses, has been created. These are of two classes—pulses that excite or invert z magnetization and those that act as general-rotation πr/2 or π pulses irrespective of the initial condition of the nuclear magnetization. It was found convenient to design the latter class as amplitude-modulated time-symmetric pulses. Tables of Fourier coefficients and pulse-shape ordinates are given for practical implementation of BURP pulses, together with the calculated frequency-domain responses and experimental verifications. Examples of the application of band-selective pulses in conventional and multidimensional spectroscopy are given. Pure-phase pulses of this type should also find applications in magnetic resonance imaging where refocusing schemes are undesirable.

  17. Quarter-wave pulse tube

    Swift, G. W.; Gardner, D. L.; Backhaus, S. N.

    2011-10-01

    In high-power pulse-tube refrigerators, the pulse tube itself can be very long without too much dissipation of acoustic power on its walls. The pressure amplitude, the volume-flow-rate amplitude, and the time phase between them evolve significantly along a pulse tube that is about a quarter-wavelength long. Proper choice of length and area makes the oscillations at the ambient end of the long pulse tube optimal for driving a second, smaller pulse-tube refrigerator, thereby utilizing the acoustic power that would typically have been dissipated in the first pulse-tube refrigerator's orifice. Experiments show that little heat is carried from the ambient heat exchanger to the cold heat exchanger in such a long pulse tube, even though the oscillations are turbulent and even when the tube is compactly coiled.

  18. How Formaldehyde Inhibits Hydrogen Evolution by [FeFe]-Hydrogenases: Determination by ¹³C ENDOR of Direct Fe-C Coordination and Order of Electron and Proton Transfers.

    Bachmeier, Andreas; Esselborn, Julian; Hexter, Suzannah V; Krämer, Tobias; Klein, Kathrin; Happe, Thomas; McGrady, John E; Myers, William K; Armstrong, Fraser A

    2015-04-29

    Formaldehyde (HCHO), a strong electrophile and a rapid and reversible inhibitor of hydrogen production by [FeFe]-hydrogenases, is used to identify the point in the catalytic cycle at which a highly reactive metal-hydrido species is formed. Investigations of the reaction of Chlamydomonas reinhardtii [FeFe]-hydrogenase with formaldehyde using pulsed-EPR techniques including electron-nuclear double resonance spectroscopy establish that formaldehyde binds close to the active site. Density functional theory calculations support an inhibited super-reduced state having a short Fe-(13)C bond in the 2Fe subsite. The adduct forms when HCHO is available to compete with H(+) transfer to a vacant, nucleophilic Fe site: had H(+) transfer already occurred, the reaction of HCHO with the Fe-hydrido species would lead to methanol, release of which is not detected. Instead, Fe-bound formaldehyde is a metal-hydrido mimic, a locked, inhibited form analogous to that in which two electrons and only one proton have transferred to the H-cluster. The results provide strong support for a mechanism in which the fastest pathway for H2 evolution involves two consecutive proton transfer steps to the H-cluster following transfer of a second electron to the active site. PMID:25871921

  19. Coiled transmission line pulse generators

    McDonald, Kenneth Fox

    2010-11-09

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

  20. Optimization of Adiabatic Selective Pulses

    Rosenfeld, Daniel; Panfil, Shimon L.; Zur, Yuval

    1997-06-01

    Adiabatic RF pulses play an important role in spin inversion due to their robust behavior in presence of inhomogeneous RF fields. These pulses are characterized by the trajectory swept by the tip of theBeffvector and the rate of motion upon it. In this paper, a method is described for optimizing adiabatic inversion pulses to achieve a frequency-selective magnetization inversion over a given bandwidth in a shorter time and to improve slice profile. An efficient adiabatic pulse is used as an initial condition. This pulse allows for flexibility in choosing its parameters; in particular, the transition sharpness may be traded off against the inverted bandwidth. The considerations for selecting the parameters of the pulse according to the requirements of the design are discussed. The optimization process then improves the slice profile by optimizing the rate of motion along the trajectory of the pulse while preserving the trajectory itself. The adiabatic behavior of the optimized pulses is fully preserved over a twofold range of variation in the RF amplitude which is sufficient for imaging applications in commercial high-field MRI machines. Design examples demonstrate the superiority of the optimized pulses over the conventional sech/tanh pulse.

  1. Versatile pulse programmer for pulsed nuclear magnetic resonance spectroscopy

    A description of the sequence of events and the decisions leading to the design of a versatile pulse programmer for pulsed NMR are presented. Background and application information is discussed in order that the reader might better understand the role of the pulse programmer in a NMR spectrometer. Various other design approaches are presented as a basis for comparison. Specifications for this design are proposed, the hardware implementation of the specifications is discussed, and the software operating system is presented

  2. Africa's Pulse, April 2015

    Chuhan-Pole, Punam; Francisco H.G. Ferreira; Calderon, Cesar; Christiaensen, Luc; Evans, David; Kambou, Gerard; Boreux, Sebastien; Korman, Vijdan; Kubota, Megumi; Buitano, Mapi

    2015-01-01

    Africa’s Pulse is a biannual publication containing an analysis of the near-term macro-economic outlook for the region. It also includes a section focusing on a topic that represents a particular development challenges for the continent. It is produced by the Office of the Chief Economist for the Africa Region.This issue is an analysis of issues shaping Africa's economic future. Growth remains stable in Sub-Saharan Africa. Some countries are seeing a slowdown, but the region's economic pros...

  3. Africa's Pulse, October 2014

    Punam, Chuhan-Pole; Ferreira, Francisco H.G.

    2014-01-01

    Africa’s Pulse is a biannual publication containing an analysis of the near-term macro-economic outlook for the region. It also includes a section focusing on a topic that represents a particular development challenges for the continent. It is produced by the Office of the Chief Economist for the Africa Region.This issue is an analysis of issues shaping Africa's economic future. Growth remains stable in Sub-Saharan Africa. Some countries are seeing a slowdown, but the region's economic pros...

  4. Pulsed neutron porosity logging

    A borehole logging tool employing a pulsed neutron source and a pair of spaced-apart epithermal neutron detectors is lowered into a borehole traversing a subsurface formation. The formation is irradiated with bursts of fast neutrons and the epithermal neutrons returning to the borehole as a result of such irradiation are detected by the pair of epithermal neutrons detectors. These detected epithermal neutrons are both time resolved and time integrated during their epithermal dieaway spectrum to provide indications of lithology independent porosity and lithology dependent porosity respectively. 6 refs

  5. Explosive pulsed power

    Altgilbers, Larry L; Freeman, Bruce L

    2010-01-01

    Explosive pulsed power generators are devices that either convert the chemical energy stored in explosives into electrical energy or use the shock waves generated by explosives to release energy stored in ferroelectric and ferromagnetic materials. The objective of this book is to acquaint the reader with the principles of operation of explosive generators and to provide details on how to design, build, and test three types of generators: flux compression, ferroelectric, and ferromagnetic generators, which are the most developed and the most near term for practical applications. Containing a co

  6. Pulse front tilt measurement of femtosecond laser pulses

    Dimitrov, Nikolay; Stoyanov, Lyubomir; Stefanov, Ivan; Dreischuh, Alexander; Hansinger, Peter; Paulus, Gerhard G.

    2016-07-01

    In this work we report experimental investigations of an intentionally introduced pulse front tilt on femtosecond laser pulses by using an inverted field correlator/interferometer. A reliable criterion for the precision in aligning (in principle) dispersionless systems for manipulating ultrashort pulses is developed, specifically including cases when the pulse front tilt is a result of a desired spatio-temporal coupling. The results obtained using two low-dispersion diffraction gratings are in good qualitative agreement with the data from a previously developed analytical model and from an independent interferometric measurement.

  7. Wave-packet dynamics in alkaline dimers. Investigation and control through coherent excitation with fs-pulses

    During my PhD thesis I investigated alkaline dimers with coherent control in a molecular beam as well as with pump-probe spectroscopy in a magneto-optical trap (MOT). The aim of the coherent control experiments were the isotope selective ionization with phase- and amplitude-shaped fs-pulses. Chapter 4 described the gained results of isotope selective ionization of NaK and KRb in a molecular beam by using different pulse formers. For the NaK dimer was the reached optimization factor RPh and Ampl770=Rmax/Rmin=25 between maximization and minimization of the isotopomer ratio (23Na39K)+/(23Na41K)+ with phase and amplitude modulation of the fs-pulse with a central wavelength of λ=770 nm. From the electronic ground-state X(1)1Σ+;ν''=0 transfers a one-photon-excitation population in the first excited A(2) 1Σ+ state. The coherent control experiment on KRb was used to maximize and minimize the isotopomer ratio (124KRb)+/(126KRb)+. It was the first coherent control experiment with a spectral resolution of 1.84 cm-1/Pixel. For the phase and amplitude optimization was the received optimization factor between minimization and maximization of the isotopomer ratio RPh and Ampl=Rmax/Rmin=7 at a central wavelength of 840 nm. The results showed a stepwise excitation process from the electronic ground-state in the first excited (2)1Σ+ state with a further excitation, that is possible over three resonant energy potential curves into the ionic ground-state. In the second part of my thesis I realized pump-probe spectroscopy of Rb2 dimers in a dark SPOT. (orig.)

  8. Compensated pulsed alternator

    This invention relates to an electromechanical energy converter with inertial energy storage. The device, a single phase, two or multi-pole alternator with stationary field coils, and a rotating armature is provided. The rotor itself may be of laminated steel for slower pulses or for faster pulses should be nonmagnetic and electrically nonconductive in order to allow rapid penetration of the field as the armature coil rotates. The armature coil comprises a plurality of power generating conductors mounted on the rotor. The alternator may also include a stationary or counterrotating compensating coil to increase the output voltage thereof and to reduce the internal impedance of the alternator at the moment of peak output. As the machine voltage rises sinusoidally, an external trigger switch is adapted to be closed at the appropriate time to create the desired output current from said alternator to an external load circuit, and as the output current passes through zero a self-commutating effect is provided to allow the switch to disconnect the generator from the external circuit

  9. Bipolar pulse forming line

    Rhodes, Mark A.

    2008-10-21

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

  10. Assembly delay line pulse generators

    1971-01-01

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

  11. Programming Pulse Driven Quantum Computers

    Lloyd, Seth

    1999-01-01

    Arrays of weakly-coupled quantum systems can be made to compute by subjecting them to a sequence of electromagnetic pulses of well-defined frequency and length. Such pulsed arrays are true quantum computers: bits can be placed in superpositions of 0 and 1, logical operations take place coherently, and dissipation is required only for error correction. Programming such computers is accomplished by selecting the proper sequence of pulses.

  12. A method of laser pulse

    Ragul' skii, V.V.; Nosach, O.U.

    1981-07-08

    A method is proposed for shaping a laser pulse by using its nonlinear interaction with the medium. In order to increase the contrast of the emission pulse over a wide spectrum range without brightness loss, the emission pulse is subjected to induced scattering in the transparent medium, while preserving the solid angle of the emission; the scattered emission is then separated from the initial emission.

  13. A microsecond pulse radiolysis apparatus

    A pulse radiolysis system built up in Beijing Radiation Center was described. Using a 5 MeV scanning linac as the pulse radiation source, the system could provide a 2 microsecond width and 200 mA single pulse. The non-interrupt beam monitor was used to monitor the beam current. A kinetic spectrophotometer was chosen to detect the transient optical absorption. A BCM-80A single board computer system with a transient signal recording board was used to record and process the signal and to control the time sequencing. Several pulse radiolysis experiments were carried out in aqueous system and positive results were obtained

  14. Pulse oximetry in severe anaemia

    Ramsing, T; Rosenberg, J

    1992-01-01

    Measurement of arterial oxygen saturation by pulse oximetry was performed in two patients with acute and chronic anaemia (haemoglobin concentrations: 2.9 mmol/l (4.7 g/dl) and 1.9 mmol/l (3.0 g/dl), respectively) using a Radiometer OXI and a Nellcor N-200 pulse oximeter. The two oximeters read...... alternating different values in the two patients. In conclusion, pulse oximeters are able to give a value for oxygen saturation even at extreme anaemia, and when a high value is given, it possibly reflects arterial oxygen saturation. The value of pulse oximetry in severe anaemia is discussed....

  15. Powerful nanosecond pulse train generator

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

  16. The Practice of Pulse Processing

    Fowler, J W; Doriese, W B; Joe, Y -I; O'Neil, G C; Ullom, J N; Swetz, D S

    2015-01-01

    The analysis of data from x-ray microcalorimeters requires great care; their excellent intrinsic energy resolution cannot usually be achieved in practice without a statistically near-optimal pulse analysis and corrections for important systematic errors. We describe the essential parts of a pulse-analysis pipeline for data from x-ray microcalorimeters, including steps taken to reduce systematic gain variation and the unwelcome dependence of filtered pulse heights on the exact pulse-arrival time. We find these steps collectively to be essential tools for getting the best results from a microcalorimeter-based x-ray spectrometer.

  17. The Practice of Pulse Processing

    Fowler, J. W.; Alpert, B. K.; Doriese, W. B.; Joe, Y.-I.; O'Neil, G. C.; Ullom, J. N.; Swetz, D. S.

    2015-12-01

    The analysis of data from X-ray microcalorimeters requires great care; their excellent intrinsic energy resolution cannot usually be achieved in practice without a statistically near-optimal pulse analysis and corrections for important systematic errors. We describe the essential parts of a pulse-analysis pipeline for data from X-ray microcalorimeters, including steps taken to reduce systematic gain variation and the unwelcome dependence of filtered pulse heights on the exact pulse-arrival time. We find these steps collectively to be essential tools for getting the best results from a microcalorimeter-based X-ray spectrometer.

  18. Klystron pulse mudulator for linac

    A highly stable klystron pulse modulator is required in constructing a linac with good beam characteristics. The De-Qing circuit has been used conventionally to stabilize the output of a pulse modulator, but this method can achieve a stability of 1 percent at best, which is far larger than the targeted stability (less than 0.1 percent). The following three types of regulators are available to stabilize the D.C. power source of a pulse modulator: series regulator, shunt regulator and switching regulator. Advantages and disadvantages of these regulators are examined and the shunt regulator is selected because of its simple circuit structure and easy adjustment. The klystron pulse modulator has the features of being able to serve as a component of a large-power pulse klystron, being high in pulse stability (reproducibility), giving good pulse profiles (free from evershoot or undershoot), being small in size, etc. The klystron pulse modulator consists of a power source step-up transfermer, three-phase full-wave rectifying circuit, smoothing circuit, constant voltage control circuit, switching circuit, PFN circuit and pulse transformer. (Nogami, K.)

  19. Theoretical Studies of the Output Pulse with Variation of the Pumping Pulse for RF Excited CO2 Pulsed Waveguide Laser

    A Rauf; ZHOU Wei; XIN Jian-guo

    2006-01-01

    The behavior of a RF-excited waveguide CO2 laser in the pulse regime is studied theoretically. The output pulse evolution is studied by applying three types of pulses namely the square, sine and the triangular ones as the excitation pulses. The frequency dependence behavior of the output pulse is also presented.

  20. Capacitor discharge pulse analysis.

    Baker, Michael Sean; Griffiths, Stewart K.; Tanner, Danelle Mary

    2013-08-01

    Capacitors used in firing sets and other high discharge current applications are discharge tested to verify performance of the capacitor against the application requirements. Parameters such as capacitance, inductance, rise time, pulse width, peak current and current reversal must be verified to ensure that the capacitor will meet the application needs. This report summarizes an analysis performed on the discharge current data to extract these parameters by fitting a second-order system model to the discharge data and using this fit to determine the resulting performance metrics. Details of the theory and implementation are presented. Using the best-fit second-order system model to extract these metrics results in less sensitivity to noise in the measured data and allows for direct extraction of the total series resistance, inductance, and capacitance.

  1. Pulsed depressed collector

    Kemp, Mark A

    2015-11-03

    A high power RF device has an electron beam cavity, a modulator, and a circuit for feed-forward energy recovery from a multi-stage depressed collector to the modulator. The electron beam cavity include a cathode, an anode, and the multi-stage depressed collector, and the modulator is configured to provide pulses to the cathode. Voltages of the electrode stages of the multi-stage depressed collector are allowed to float as determined by fixed impedances seen by the electrode stages. The energy recovery circuit includes a storage capacitor that dynamically biases potentials of the electrode stages of the multi-stage depressed collector and provides recovered energy from the electrode stages of the multi-stage depressed collector to the modulator. The circuit may also include a step-down transformer, where the electrode stages of the multi-stage depressed collector are electrically connected to separate taps on the step-down transformer.

  2. Pulse-shaping strategies in short-pulse fiber amplifiers

    Ultrashort pulse lasers are an important tool in scientific and industrial applications. However, many applications are demanding higher average powers from these ultrashort pulse sources. This can be achieved by combining direct diode pumping with novel gain media designs. In particular, ultrashort pulse fiber lasers are now delivering average powers in the kW range. However, the design of fiber lasers, producing pulses with high peak-powers, is challenging due to the impact of nonlinear effects. To significantly reduce these detrimental effects in ultrashort pulse fiber amplifers, the combination of chirped pulse amplification (CPA) and large mode area fibers is employed. Using these methods, the pulse energy of fiber lasers has been steadily increasing for the past few years. Recently, a fiber-based CPA-system has been demonstrated which produces pulse energies of around 1 mJ. However, both the stretching and the enlargement of the mode area are limited, and therefore, the impact of nonlinearity is still noticed in systems employing such devices. The aim of this thesis is the analysis of CPA-systems operated beyond the conventional nonlinear limit, which corresponds to accumulated nonlinear phase-shifts around 1 rad. This includes a detailed discussion of the influence of the nonlinear effect self-phase modulation on the output pulse of CPA-systems. An analytical model is presented. Emphasis is placed on the design of novel concepts to control the impact of self-phase modulation. Pulse-shaping is regarded as a powerful tool to accomplish this goal. Novel methods to control the impact of SPM are experimentally demonstrated. The design of these concepts is based on the theoretical findings. Both amplitude- and phase-shaping are studied. Model-based phase-shaping is implemented in a state-of-the-art fiber CPA-system. The influence of the polarization state is also highlighted. Additionally, existing techniques and recent advances are put into context. (orig.)

  3. Pulse-shaping strategies in short-pulse fiber amplifiers

    Schimpf, Damian Nikolaus

    2010-02-09

    Ultrashort pulse lasers are an important tool in scientific and industrial applications. However, many applications are demanding higher average powers from these ultrashort pulse sources. This can be achieved by combining direct diode pumping with novel gain media designs. In particular, ultrashort pulse fiber lasers are now delivering average powers in the kW range. However, the design of fiber lasers, producing pulses with high peak-powers, is challenging due to the impact of nonlinear effects. To significantly reduce these detrimental effects in ultrashort pulse fiber amplifers, the combination of chirped pulse amplification (CPA) and large mode area fibers is employed. Using these methods, the pulse energy of fiber lasers has been steadily increasing for the past few years. Recently, a fiber-based CPA-system has been demonstrated which produces pulse energies of around 1 mJ. However, both the stretching and the enlargement of the mode area are limited, and therefore, the impact of nonlinearity is still noticed in systems employing such devices. The aim of this thesis is the analysis of CPA-systems operated beyond the conventional nonlinear limit, which corresponds to accumulated nonlinear phase-shifts around 1 rad. This includes a detailed discussion of the influence of the nonlinear effect self-phase modulation on the output pulse of CPA-systems. An analytical model is presented. Emphasis is placed on the design of novel concepts to control the impact of self-phase modulation. Pulse-shaping is regarded as a powerful tool to accomplish this goal. Novel methods to control the impact of SPM are experimentally demonstrated. The design of these concepts is based on the theoretical findings. Both amplitude- and phase-shaping are studied. Model-based phase-shaping is implemented in a state-of-the-art fiber CPA-system. The influence of the polarization state is also highlighted. Additionally, existing techniques and recent advances are put into context. (orig.)

  4. Nonlinear Femtosecond Pulse Reshaping in Waveguide Arrays

    Darren D. Hudson; Shish, Kimberlee; Schibli, Thomas R.; Kutz, J. Nathan; Christodoulides, Demetrios N.; Morandotti, Roberto; Cundiff, Steven T.

    2008-01-01

    We observe nonlinear pulse reshaping of femtosecond pulses in a waveguide array due to coupling between waveguides. Amplified pulses from a mode-locked fiber laser are coupled to an AlGaAs core waveguide array structure. The observed power-dependent pulse reshaping agrees with theory, including shortening of the pulse in the central waveguide.

  5. A Single-Pulse Integrator

    Miller, Arne

    1974-01-01

    A single-pulse integrator is described. It gives a relative measure of the integral of the output signal from a coil monitor on the Risø 10 MeV linear accelerator, and displays the value on a digital voltmeter. The reproduccibility is found to be better than ±1% for an accelerated pulse charge...

  6. How to measure the pulse

    Dianne Pickering

    2013-01-01

    Before surgery, eye patients must be assessed for their suitability for surgery. Taking the pulse allows us to find out what the patient’s heart rate is and to assess the strength, regularity, and character of the pulse. Irregularities might indicate a heart problem and must be investigated.

  7. Pulse oximetry for perioperative monitoring

    Pedersen, Tom; Møller, Ann Merete; Hovhannisyan, Karen

    Pulse oximetry is extensively used in the perioperative period and might improve patient outcomes by enabling an early diagnosis and, consequently, correction of perioperative events that might cause postoperative complications or even death. Only a few randomized clinical trials of pulse oximetry...

  8. NMR in pulsed magnetic field

    Abou-Hamad, Edy

    2011-09-01

    Nuclear magnetic resonance (NMR) experiments in pulsed magnetic fields up to 30.4 T focused on 1H and 93Nb nuclei are reported. Here we discuss the advantage and limitation of pulsed field NMR and why this technique is able to become a promising research tool. © 2011 Elsevier Inc. All Rights Reserved.

  9. Neurostimulation using subnanosecond electric pulses

    Xiao, Shu; Pakhomov, Andrei; Guo, Fei; Polisetty, Swetha; Schoenbach, Karl H.

    2013-02-01

    We have for the first time recorded action potentials in rat hippocampus neurons when they were stimulated by subnanosecond electric pulses. The preliminary results show that applying a series of pulses allowed the accumulation of depolarization before activating the voltage gated channels. The depolarization only occurred when the electric pulses were applied. It is unclear whether the depolarization is caused by the charge accumulation across the membrane or the cation influx due to the membrane permeabilization. We have also conducted an electromagnetic simulation of delivering subnanosecond pulses to tissues using an impulse radiating antenna. The results show that the pulses can be confined in the deep region in the brain but the amplitude is reduced significantly due to the attenuation of the tissues. A partially lossy dielectric lens may be used to reverse the decreasing trend of the electric field.

  10. Pulse modulated microwave plasma etching

    The authors report the etching characteristics of silicon and silicon dioxide studied in an anisotropic microwave plasma etching system having a variably pulsed microwave source. Pulse frequency, as well as pulse duty cycle, can be varied on the microwave source. Earlier work done in isotropic rf systems suggests that etch rate and quality may be affected positively by pulse modulation. Electron-cyclotron resonance heating is used so that the process gas (sulfur hexafluoride) can be more efficiently ionized, with the resulting ions and free radicals from the plasma then etching the silicon substrate or the silicon dioxide on the substrate. Characteristics being examined include etch rate, etch anisotropy, and etching selectivity between silicon and silicon dioxide. The design of the microwave plasma etching system, including the variable pulsed microwave source, are presented along with preliminary results

  11. Pre-earthquake Magnetic Pulses

    Scoville, John; Freund, Friedemann

    2014-01-01

    A semiconductor model of rocks is shown to describe unipolar magnetic pulses, a phenomenon that has been observed prior to earthquakes. These pulses are observable because their extremely long wavelength allows them to pass through the Earth's crust. Interestingly, the source of these pulses may be triangulated to pinpoint locations where stress is building deep within the crust. We couple a semiconductor drift-diffusion model to a magnetic field in order to describe the electromagnetic effects associated with electrical currents flowing within rocks. The resulting system of equations is solved numerically and it is seen that a volume of rock may act as a diode that produces transient currents when it switches bias. These unidirectional currents are expected to produce transient unipolar magnetic pulses similar in form, amplitude, and duration to those observed before earthquakes, and this suggests that the pulses could be the result of geophysical semiconductor processes.

  12. A trial of Fe(Se{sub 1-x}Te{sub x}) thin film fabrication by pulsed laser deposition using ArF excimer laser

    Yoshimoto, T; Kiss, T; Inoue, M; Kai, H; Teranishi, R; Mori, N; Mukaida, M [Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan); Ichino, Y; Yoshida, Y [Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan); Matsumoto, K [Kyushu Institute of Technology, 1-1 Sensui-cho, Tobata-ku, Kitakyushu, Fukuoka, 804-8550 (Japan); Ichinose, A, E-mail: yoshimoto07@zaiko10.zaiko.kyushu-u.ac.j [Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka, Kanagawa 240-0196 (Japan)

    2010-06-01

    We fabricated Fe(Se{sub 1-x}Te{sub x}) thin films on LSAT(100), MgO(001), R-Al{sub 2}O{sub 3} substrates by ArF excimer pulsed laser deposition (ArF-PLD) and investigated pulse repetition rate dependence on film growth of Fe(Se{sub 1-x}Te{sub x}) thin films in ArF-PLD. Through x-ray diffraction measurements of Fe(Se{sub 1-x}Te{sub x}) thin films grown by ArF-PLD, 00l peaks of Fe(Se{sub 1-x}Te{sub x}) were confirmed in Fe(Se{sub 1-x}Te{sub x}) thin films grown by pulse repetition rate of 10 Hz but the 00l peaks were not confirmed in Fe(Se{sub 1-x}Te{sub x}) thin films grown at 5 Hz. Atomic force microscopy (AFM) revealed that 100 {approx} 250 nm sized grains were formed on surface of the thin films grown at 10 Hz. It was found that the thin films grown at 5 Hz were formed thinner than those grown at 10 Hz, in spite of the same pulses. Energy dispersive x-ray spectroscopy (EDX) analysis revealed that composition elements of the thin films grown at 5 Hz were re-evaporated from them more than those grown at 10Hz. In {rho}-T measurements of the thin films grown at 10 Hz, it was confirmed that the thin films has T{sub Conset} = 6.5 {approx} 10.5 K and T{sub C0} of the Fe(Se{sub 1-x}Te{sub x}) thin film on an MgO substrate is 3.9 K.

  13. A model for the dissociation pulse, afterglow, and laser pulse in the Cu/CuCl double pulse laser

    Kushner, M J; Culick, F. E. C.

    1980-01-01

    A model which completely describes the Cu/CuCl double pulse laser is presented. The dissociation discharge pulse and afterglow are simulated and the results are used as initial conditions for an analysis of the pumping discharge pulse and laser pulse. Experimental behavior including the minimum, optimum, and maximum delays between pulses, and the dependence of laser pulse energy on dissociation energy are satisfactorily reproduced. An optimum tube temperature is calculated, and the dependence...

  14. A model for the dissociation pulse, afterglow, and laser pulse in the Cu/CuCI double pulse laser

    Kushner, M J; Culick, F. E. C.

    1980-01-01

    A model which completely describes the Cu/CuCI double pulse laser is presented. The dissociation discharge pulse and afterglow are simulated and the results are used as initial conditions for an analysis of the pumping discharge pulse and laser pulse. Experimental behavior including the minimum, optimum, and maximum delays between pulses, and the dependence of laser pulse energy on dissociation energy are satisfactorily reproduced. An optimum tube temperature is calculated, and the depende...

  15. Pulse on pulse: modulation and signification in Rafael Lozano-Hemmer's Pulse Room

    Merete Carlson

    2012-06-01

    Full Text Available This article investigates the relation between signifying processes and non-signifying material dynamism in the installation Pulse Room (2006 by Mexican Canadian artist Rafael Lozano-Hemmer. In Pulse Room the sense of pulse is ambiguous. Biorhythms are transmitted from the pulsing energy of the visitor's beating heart to the flashing of a fragile light bulb, thereby transforming each light bulb into a register of individual life. But at the same time the flashing light bulbs together produce a chaotically flickering light environment composed by various layers of repetitive rhythms, a vibrant and pulsating “room”. Hence, the visitor in Pulse Room is invited into a complex scenario that continuously oscillates between various aspects of signification (the light bulbs representing individual lives; the pulse itself as the symbolic “rhythm of life” and instants of pure material processuality (flickering light bulbs; polyrhythmic layers. Taking our point of departure in a discussion of Gilles Deleuze's concepts of modulation and signaletic material in relation to electronic media, we examine how the complex orchestration of pulsation between signification and material modulation produces a multilayered sense of time and space that is central to the sensory experience of Pulse Room as a whole. Pulse Room is, at the very same time, a relational subject–object intimacy and an all-encompassing immersive environment modulating continuously in real space-time.

  16. Pulse Detonation Engine Modeled

    Paxson, Daniel E.

    2001-01-01

    Pulse Detonation Engine Technology is currently being investigated at Glenn for both airbreathing and rocket propulsion applications. The potential for both mechanical simplicity and high efficiency due to the inherent near-constant-volume combustion process, may make Pulse Detonation Engines (PDE's) well suited for a number of mission profiles. Assessment of PDE cycles requires a simulation capability that is both fast and accurate. It should capture the essential physics of the system, yet run at speeds that allow parametric analysis. A quasi-one-dimensional, computational-fluid-dynamics-based simulation has been developed that may meet these requirements. The Euler equations of mass, momentum, and energy have been used along with a single reactive species transport equation, and submodels to account for dominant loss mechanisms (e.g., viscous losses, heat transfer, and valving) to successfully simulate PDE cycles. A high-resolution numerical integration scheme was chosen to capture the discontinuities associated with detonation, and robust boundary condition procedures were incorporated to accommodate flow reversals that may arise during a given cycle. The accompanying graphs compare experimentally measured and computed performance over a range of operating conditions for a particular PDE. Experimental data were supplied by Fred Schauer and Jeff Stutrud from the Air Force Research Laboratory at Wright-Patterson AFB and by Royce Bradley from Innovative Scientific Solutions, Inc. The left graph shows thrust and specific impulse, Isp, as functions of equivalence ratio for a PDE cycle in which the tube is completely filled with a detonable hydrogen/air mixture. The right graph shows thrust and specific impulse as functions of the fraction of the tube that is filled with a stoichiometric mixture of hydrogen and air. For both figures, the operating frequency was 16 Hz. The agreement between measured and computed values is quite good, both in terms of trend and

  17. Pulse source requirements for OTDM systems

    Clausen, Anders; Poulsen, Henrik Nørskov; Oxenløwe, Leif Katsuo;

    2003-01-01

    A simulation model for investigating the impact of incoherent crosstalk due to pulse tail overlapping is proposed. Requirements to pulse width and pulse tail extinction ratio introducing a maximum of 1 dB penalty is extracted.......A simulation model for investigating the impact of incoherent crosstalk due to pulse tail overlapping is proposed. Requirements to pulse width and pulse tail extinction ratio introducing a maximum of 1 dB penalty is extracted....

  18. Pulsed noise analysis system

    Barsanti, M.L. [Naval Research Lab., Washington, DC (United States); Smutek, L.S. [Mission Research Corp., Newington, VA (United States); Armstrong, C.M. [Northrop Grumman Corp., Rolling Meadows, IL (United States)

    1995-12-31

    NRL studies of various microwave and millimeter wave amplifiers and the need to know and understand their characteristics have led to the development of a pulsed noise analysis system. This system is capable of measuring amplitude, phase, and total spectra of two signals simultaneously. It can also measure am/pm conversion, group or phase delay and linearity, and phase and amplitude jitter. The system downconverts the signal to be analyzed and then digitizes the intermediate frequency. The digitized sample is transferred to a personal computer equipped with LabVIEW, where all further processing and analysis takes place. It is digitally demodulated into I and Q channels which can then be separated into amplitude and phase information. Discrete Fourier Transforms are used to display the spectral information. Measurements have been performed on both conventional linear beam devices such as commercially available TWT and klystron amplifiers. As well as two gyro-devices, the NRL gyroklystron and gyrotwystron amplifiers. These measurements were expanded to include noise power dependency on various tube parameters such as beam current and alpha. The results of the analysis will be used as a basis for modifying the gyrotwystron amplifier to improve its operating characteristics.

  19. Magnetic Alignment of Pulsed Solenoids Using the Pulsed Wire Method

    Arbelaez, D.; Madur, A.; Lipton, T.M.; Waldron, W.L.; Kwan, J.W.

    2011-04-01

    A unique application of the pulsed-wire measurement method has been implemented for alignment of 2.5 T pulsed solenoid magnets. The magnetic axis measurement has been shown to have a resolution of better than 25 {micro}m. The accuracy of the technique allows for the identification of inherent field errors due to, for example, the winding layer transitions and the current leads. The alignment system is developed for the induction accelerator NDCX-II under construction at LBNL, an upgraded Neutralized Drift Compression experiment for research on warm dense matter and heavy ion fusion. Precise alignment is essential for NDCX-II, since the ion beam has a large energy spread associated with the rapid pulse compression such that misalignments lead to corkscrew deformation of the beam and reduced intensity at focus. The ability to align the magnetic axis of the pulsed solenoids to within 100 pm of the induction cell axis has been demonstrated.

  20. Magnetic Alignment of Pulsed Solenoids Using the Pulsed Wire Method

    A unique application of the pulsed-wire measurement method has been implemented for alignment of 2.5 T pulsed solenoid magnets. The magnetic axis measurement has been shown to have a resolution of better than 25 (micro)m. The accuracy of the technique allows for the identification of inherent field errors due to, for example, the winding layer transitions and the current leads. The alignment system is developed for the induction accelerator NDCX-II under construction at LBNL, an upgraded Neutralized Drift Compression experiment for research on warm dense matter and heavy ion fusion. Precise alignment is essential for NDCX-II, since the ion beam has a large energy spread associated with the rapid pulse compression such that misalignments lead to corkscrew deformation of the beam and reduced intensity at focus. The ability to align the magnetic axis of the pulsed solenoids to within 100 pm of the induction cell axis has been demonstrated.

  1. Preliminary Study of Pulsed Powering

    Hasib, A; The ATLAS collaboration; Gutierrez, P

    2013-01-01

    The standard solution for powering the electronics of particle physics detectors is to supply direct current. In this report, we investigate several advantages of using a Pulsed Powering scheme. Pulsed Powering could achieve 2-wire, point-of-load voltage regulation over typical low voltage power cables. This could be a reliable and serviceable solution for point of load voltage regulation in the high radiation environment of the High Luminosity Large Hadron Collider. Pulsed Powering might also be exploited to provide an inexpensive solution for the elimination of voltage offsets among ATLAS Pixel Detector subsystems and new low mass techniques for distributing power to particle detectors.

  2. Pulsed ultrasonic stir welding method

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    A method of performing ultrasonic stir welding uses a welding head assembly to include a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. In the method, the rod is rotated about its longitudinal axis during a welding operation. During the welding operation, a series of on-off ultrasonic pulses are applied to the rod such that they propagate parallel to the rod's longitudinal axis. At least a pulse rate associated with the on-off ultrasonic pulses is controlled.

  3. Hyper dispersion pulse compressor for chirped pulse amplification systems

    Barty, Christopher P. J.

    2011-11-29

    A grating pulse compressor configuration is introduced for increasing the optical dispersion for a given footprint and to make practical the application for chirped pulse amplification (CPA) to quasi-narrow bandwidth materials, such as Nd:YAG. The grating configurations often use cascaded pairs of gratings to increase angular dispersion an order of magnitude or more. Increased angular dispersion allows for decreased grating separation and a smaller compressor footprint.

  4. Pulsed Corona for Sustainable Technology

    Highly active coronas with a peak power of up to 25 MW p/m corona wire and kJ/liter energy densities in the streamer channels can be produced by pulsed power. Since the voltage pulses are short, full breakdown does not occur even though the discharge currents are hundreds of Amperes. A matched pulsed power source can deposit up to 80% of its electrical energy into such a controlled discharge. Reliable and efficient sources characterized by 100 kV,150 ns wide pulses at 1000 Hz have passed 400 hours of operation. The area of applications is growing: VOC control, hot gas cleanup, water and air purification and sterilization. (author)

  5. Next generation Chirped Pulse Amplification

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

    1998-03-01

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

  6. Xi'an pulsed reactor

    Xi'an Pulsed Reactor (XAPR) Designed and constructed all by China is first research pulsed reactor with versatile applications. It is characterized with inherent safety, versatile application, structure simplicity and convenience for operation. It can be operated not only at stead-state but also at pulse mode as well as square wave mode. The rated power to the reactor under steady-state operation is 2 MW and the reactor is operated under pulsing state, its maximum peak power is about 4200 MW. XAPR is also equipped with many kinds of the experimental and irradiation facilities. The applications are radio-isotopes production, neutron activity analysis, neutron radiograph, monocrystalline silicon irradiation, material irradiation test, nuclear physics, neutron physics and nuclear chemistry studies, teaching and training. The XAPR has went into test operation and application for nearly two years that has shown its advantage and extensiveness

  7. Repetitively pulsed vacuum insulator flashover

    Experiments were performed to determine the flashover strength of various vacuum insulators under conditions of repetitive pulsing. The pulse duration was 30 ns, and the thickness of a typical insulator sample was 1.8 cm. Data were taken for 450 insulators from five different materials. An insulator was subjected to an extended series of pulses at a given repetition rate and field. If flashover was not detected, the field level was increased and the sequence repeated. At rates up to 50 pulses per second, there was no apparent dependence of flashover field on rate. In addition, some ''single shot'' data were taken, including various modifications of the geometries and surface textures of the insulators. Only two to the modifications increased the flashover strength significantly over that of a 450 sample: (1) annealing some plastics (roughly a 35% increase), and (2) extending the insulator to cover the surfaces of both electrodes (an increase of nearly a factor of two)

  8. Rapidly pulsed helium droplet source

    Pentlehner, Dominik; Riechers, Ricarda; Dick, Bernhard; Slenczka, Alkwin [Institute for Physical and Theoretical Chemistry, University of Regensburg, 93053 Regensburg (Germany); Even, Uzi; Lavie, Nachum; Brown, Raviv; Luria, Kfir [Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv (Israel)

    2009-04-15

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

  9. Artistic Representation with Pulsed Holography

    This thesis describes artistic representation through pulsed holography. One of the prevalent practical problems in making holograms is object movement. Any movement of the object or film, including movement caused by acoustic vibration, has the same fatal results. One way of reducing the chance of movement is by ensuring that the exposure is very quick; using a pulsed laser can fulfill this objective. The attractiveness of using pulsed laser is based on the variety of materials or objects that can be recorded (e.g., liquid material or instantaneous scene of a moving object). One of the most interesting points about pulsed holograms is that some reconstructed images present us with completely different views of the real world. For example, the holographic image of liquid material does not appear fluid; it looks like a piece of hard glass that would produce a sharp sound upon tapping. In everyday life, we are unfamiliar with such an instantaneous scene. On the other hand, soft-textured materials such as a feather or wool differ from liquids when observed through holography. Using a pulsed hologram, we can sense the soft touch of the object or material with the help of realistic three-dimensional (3-D) images. The images allow us to realize the sense of touch in a way that resembles touching real objects. I had the opportunity to use a pulsed ruby laser soon after I started to work in the field of holography in 1979. Since then, I have made pulsed holograms of activities, including pouring water, breaking eggs, blowing soap bubbles, and scattering feathers and popcorn. I have also created holographic art with materials and objects, such as silk fiber, fabric, balloons, glass, flowers, and even the human body. Whenever I create art, I like to present the spectator with a new experience in perception. Therefore, I would like to introduce my experimental artwork through those pulsed holograms.

  10. Pulsed feedback defers cellular differentiation.

    Joe H Levine

    2012-01-01

    Full Text Available Environmental signals induce diverse cellular differentiation programs. In certain systems, cells defer differentiation for extended time periods after the signal appears, proliferating through multiple rounds of cell division before committing to a new fate. How can cells set a deferral time much longer than the cell cycle? Here we study Bacillus subtilis cells that respond to sudden nutrient limitation with multiple rounds of growth and division before differentiating into spores. A well-characterized genetic circuit controls the concentration and phosphorylation of the master regulator Spo0A, which rises to a critical concentration to initiate sporulation. However, it remains unclear how this circuit enables cells to defer sporulation for multiple cell cycles. Using quantitative time-lapse fluorescence microscopy of Spo0A dynamics in individual cells, we observed pulses of Spo0A phosphorylation at a characteristic cell cycle phase. Pulse amplitudes grew systematically and cell-autonomously over multiple cell cycles leading up to sporulation. This pulse growth required a key positive feedback loop involving the sporulation kinases, without which the deferral of sporulation became ultrasensitive to kinase expression. Thus, deferral is controlled by a pulsed positive feedback loop in which kinase expression is activated by pulses of Spo0A phosphorylation. This pulsed positive feedback architecture provides a more robust mechanism for setting deferral times than constitutive kinase expression. Finally, using mathematical modeling, we show how pulsing and time delays together enable "polyphasic" positive feedback, in which different parts of a feedback loop are active at different times. Polyphasic feedback can enable more accurate tuning of long deferral times. Together, these results suggest that Bacillus subtilis uses a pulsed positive feedback loop to implement a "timer" that operates over timescales much longer than a cell cycle.

  11. Optical pulses, lasers, measuring techniques

    Früngel, Frank B A

    1965-01-01

    High Speed Pulse Technology: Volume II: Optical Pulses - Lasers - Measuring Techniques focuses on the theoretical and engineering problems that result from the capacitor discharge technique.This book is organized into three main topics: light flash production from a capacitive energy storage; signal transmission and ranging systems by capacitor discharges and lasers; and impulse measuring technique. This text specifically discusses the air spark under atmospheric conditions, industrial equipment for laser flashing, and claims for light transmitting system. The application of light impulse sign

  12. Pulsed ultrasonic stir welding system

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    An ultrasonic stir welding system includes a welding head assembly having a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. During a welding operation, ultrasonic pulses are applied to the rod as it rotates about its longitudinal axis. The ultrasonic pulses are applied in such a way that they propagate parallel to the longitudinal axis of the rod.

  13. The Toulouse pulsed magnet facility

    The 'Laboratoire National des Champs Magnetiques Pulses' (LNCMP) is an international user facility providing access to pulsed magnetic fields up to and beyond 60 T. The laboratory disposes of 10 magnet stations equipped with long-pulse magnets operating in the 35-60 T range and a short-pulse system reaching magnetic fields in excess of 70 T. The experimental infrastructure includes various high and low-temperature systems ranging from ordinary flow-type cryostats to dilution refrigerators reaching 50 mK, as well as different types of high-pressure cells. Experimental techniques include magnetization, transport, luminescence, IR-spectroscopy and polarimetry. The LNCMP pursues an extensive in-house research program focussing on all technological and scientific aspects of pulsed magnetic fields. Recent technical developments include the implementation of 60 T rapid-cooling coils, an 80 T prototype, a pulsed dipole magnet for optical investigations of dilute matter and a transportable horizontal access magnet for small angle x-ray scattering experiments. Scientific activities cover a variety of domains, including correlated electron systems, magnetism, semiconductors and nanoscience

  14. Assessment of pulse rate variability by the method of pulse frequency demodulation

    Ohte Nobuyuki; Kamiya Atsunori; Barros Allan; Hayano Junichiro; Yasuma Fumihiko

    2005-01-01

    Abstract Background Due to its easy applicability, pulse wave has been proposed as a surrogate of electrocardiogram (ECG) for the analysis of heart rate variability (HRV). However, its smoother waveform precludes accurate measurement of pulse-to-pulse interval by fiducial-point algorithms. Here we report a pulse frequency demodulation (PFDM) technique as a method for extracting instantaneous pulse rate function directly from pulse wave signal and its usefulness for assessing pulse rate variab...

  15. Matching of pulse forming network and pulse transformer parameters in pulse modulator circuits for a klystron power supply

    The most widespread circuit of high-power microsecond pulse generation for a power supply of various pulse microwave devices is the circuit of line type modulator on the basic of an artificial pulse forming network (PFN), switch and step-up pulse transformer (PT). The basic parameters having influence on the pulse rise and fall times are time constant of a transformer circuit, PFN type, and number of its cells. The paper deals with a choice of the specified parameters

  16. A nanosecond pulsed accelerator facility

    The operation and performance of a 3-MeV pulsed electrostatic generator producing 1-ns (10-9 s) pulses is described. The system employs terminal pulsing and post-acceleration time-compression to achieve short pulses and high average current. The specifications for this system were based on the following considerations. A 10-μA average beam current represents a reasonable limit based on the ability of a target to dissipate beam power, the 1-ns pulse-length was consistent with other factors such as detector response, energy homogeneity, etc. which determine over-all time resolution, and a repetition rate of 1 MHz/s gives a duty factor consistent with the current capabilities of existing accelerator ion sources. The system consists of a terminal pulsing component which produces pulses of 10 ns in duration by sweeping a beam over an aperture located at the entrance to an accelerator tube. An average output of a current of 10 μA requires a source capable of producing 1 mA of atomic ions. After acceleration this pulse is compressed to 1 ns by the scheme suggested by Mobley. This involves sweeping the beam with proper synchronization across the aperture of a 90o doubly-focusing deflection magnet so that the early portion of the pulse travels through a longer trajectory thani the later portions, thus achieving time compression when the beam is brought to a focus on a suitable target. The radius of beam curvature in the compression magnet is 30 in and the over-all beam divergence at the target is 5o. The choice of these parameters and the effect of the deflection scheme in the beam-energy homogeneity will be discussed. Using existing nanosecond detector techniques, this system has produced over-all system resolutions of 1 ns full-width at half-maximum for both gamma rays and neutrons. It is not yet known what component or components of the system determine the limits on the time resolution of the system. As a facility for investigating neutron inelastic scattering and

  17. The pulsed reactor and its application

    The situation of the first pulsed reactor in China is briefly described. The pulsed reactor has a large prompt negative temperature coefficient of reactivity provided by combination of the uranium-zirconium hydride fuel and the moderator. Therefore, its most outstanding features are 'inherent safety' and fairly high pulsed-power capacity. The pulsed reactor is now extensively used in science and technology

  18. Experimental research on pulse forming based on high-temperature SMES applied in pulsed power

    Zhou, Yusheng; Kuang, Jianghua; Tang, Yuejin; Song, Meng; Wei, Bin; Cheng, Shijie; Pan, Yuan

    2009-03-01

    To research the key problems of storage energy and pulse forming in pulsed power, a pulse magnet made of Bi2223/Ag high-temperature superconducting (HTS) tapes applied in pulsed power experiment was developed. After determining electromagnetic characteristics of the magnet, a pulse forming network was designed. HTS magnet was immersed in liquid nitrogen bath, experiments were carried out about discharging pulse current to resistance load based on HTS magnet energy storage (SMES). The results show that pulse current waves were obtained through adjusted circuit construction and magnet parameters by acting delay of switches in the pulse forming network. The technical schemes about pulse forming based on SMES were presented.

  19. Three-Level 48-Pulse STATCOM with Pulse Width Modulation

    Singh, Bhim; Srinivas, Kadagala Venkata

    2016-03-01

    In this paper, a new control strategy of a three-level 48-pulse static synchronous compensator (STATCOM) is proposed with a constant dc link voltage and pulse width modulation at fundamental frequency switching. The proposed STATCOM is realized using eight units of three-level voltage source converters (VSCs) to form a three-level 48-pulse STATCOM. The conduction angle of each three-level VSC is modulated to control the ac converter output voltage, which controls the reactive power of the STATCOM. A fuzzy logic controller is used to control the STATCOM. The dynamic performance of the STATCOM is studied for the control of the reference reactive power, the reference terminal voltage and under the switching of inductive and capacitive loads.

  20. The coherent artifact in modern pulse measurements

    Ratner, Justin; Wong, Tsz Chun; Bartels, Randy; Trebino, Rick

    2012-01-01

    We simulate multi-shot intensity-and-phase measurements of unstable ultrashort-pulse trains using frequency-resolved-optical-gating (FROG) and spectral phase interferometry for direct electric-field reconstruction (SPIDER). Both techniques fail to reveal the pulse structure. FROG yields the average pulse duration and suggests the instability by exhibiting disagreement between measured and retrieved traces. SPIDER under-estimates the average pulse duration but retrieves the correct average pulse spectral phase. An analytical calculation confirms this behavior.

  1. Spin-mapping of Coal Structures with ESE and ENDOR

    Belford, R. L.; Clarkson, R. B.

    1989-12-01

    The broad goals of this project are to determine by nondestructive magnetic resonance methods chemical and physical structural characteristics of organic parts of native and treated coals. In this project period, we have begun to explore a technique which promises to enable us to follow to course of coal cleaning processes with microscopic spatial resolution. For the past five years, our laboratory has worked on extensions of the EPR technique as applied to coal to address these analytical problems. In this report we (1) describe the world's first nuclear magnetic resonance imaging results from an Illinois {number sign}6 coal and (2) transmit a manuscript describing how organic sulfur affect the very-high-frequency EPR spectra of coals. Magnetic resonance imaging (MRI) is a non-destructive technique that has found wide medical application as a means of visualizing the interior of human bodies. We have used MRI techniques to study the diffusion of an organic solvent (DMSO) into the pores of Illinois {number sign}6 coal. Proton MRI images reveal that this solvent at room temperature does not penetrate approximately 30% of the coal volume. Regions of the coal that exclude solvent could be related to inertinite and mineral components. A multi-technique imaging program is contemplated.

  2. Laparoscopic appendicectomy using endo-ring applicator and fallope rings

    Ali Iyoob

    2009-01-01

    Full Text Available Background/Aim: Wider adoption of laparoscopic appendicectomy (LA is limited by problems in securing the appendiceal base as well as the cost and the duration compared with the open procedure. The objective of this study was to assess the feasibility and efficacy of a new method for securing the appendiceal base in LA, so as to make the entire procedure simpler and cheaper, and hence, more popular. Methods: Twenty-five patients who were candidates for appendicectomy (emergency as well as elective and willing for the laparoscopic procedure were selected for this study. Ports used were 10 mm at the umbilicus, 5 mm at the lower right iliac fossa, and 10 mm at the left iliac fossa. Extremely friable, ruptured, or turgid organs of diameters larger than 8 mm were excluded from the study. The mesoappendix was divided close to the appendix by diathermy. Fallope rings were applied to the appendiceal base using a special ring applicator, and the appendix was divided and extracted through the lumen of the applicator. Results: The procedure was successful in 23 (92% cases, and the mean duration of the procedure was 20 minutes (15-32 minutes. There were no procedural complications seen during a median follow-up of two weeks. The equipment and rings were cheaper when compared with that of the standard methods of securing the base of the appendix. Conclusion: LA using fallope rings is a safe, simple, easy-to-learn, and economically viable method.

  3. Wide Range SET Pulse Measurement

    Shuler, Robert L.; Chen, Li

    2012-01-01

    A method for measuring a wide range of SET pulses is demonstrated. Use of dynamic logic, faster than ordinary CMOS, allows capture of short pulses. A weighted binning of SET lengths allows measurement of a wide range of pulse lengths with compact circuitry. A pulse-length-conservative pulse combiner tree routes SETs from combinational logic to the measurement circuit, allowing SET measurements in circuits that cannot easily be arranged in long chains. The method is applied to add-multiplex combinational logic, and to an array of NFET routing switches, at .35 micron. Pulses are captured in a chain of Domino Logic AND gates. Propagation through the chain is frozen on the trailing edge by dropping low the second "enable" input to the AND gates. Capacitive loading is increased in the latter stages to create an approximately logarithmic weighted binning, so that a broad range of pulse lengths can be captured with a 10 stage capture chain. Simulations show pulses can be captured which are 1/5th the length of those typically captured with leading edge triggered latch methods, and less than the length of those captured with a trailing edge latch method. After capture, the pulse pattern is transferred to an SEU protected shift register for readout. 64 instances of each of two types of logic are used as targets. One is a full adder with a 4 to 1 mux on its inputs. The other is a 4 x 4 NFET routing matrix. The outputs are passed through buffered XNOR comparators to identify pulses, which are merged in a buffered not-nand (OR) tree designed to avoid pulse absorption as much as possible. The output from each of the two test circuits are input into separate pulse measurement circuits. Test inputs were provided so that the circuit could be bench tested and calibrated. A third SET measurement circuit with no inputs was used to judge the contribution from direct hits on the measurement circuit. Heavy ions were used with an LET range from 12 to 176. At LET of 21 and below, the very

  4. Pulsed Energy Storage System Design

    Biallis, G.; Cassel, R.L.; Fowler, W.; Livdahl, P.V.; Mills, F.E.; Palmer, M.L.; Reardon, P.J.; Snowden, S.C.; Strauss, B.P.; Teng, L.C.; Winje, R.A.; /Fermilab /Wisconsin U., Madison

    1974-07-01

    A superconductive energy storage magnet which is connected to the three phase power system could be designed, constructed, and placed in operation at Fermilab which would essentially eliminate the large repetitive power pulses now required from the power system. In addition to the power pulses, voltage flicker is also caused due to the reactive power pulsation. Specifically, a one megawatt hour superconductive energy storage magnet and a 2.00 megawatt thyristorized converter can achieve nullification of these power pulses up to 400 GEV synchrotron operation. Above 400 GEV, operation should be possible up to 500 GEV with appreciable less power pulsing requirements from the system than are now considered permissible. Carried to successful completion, this project would serve to advance applied superconductivity to a highly significant degree. The effect would be of world wide importance to both high energy physics and to the electric power industry. The preliminary magnet design is a 1 MWh dipole composed of cryogenically stable composite conductors connected in parallel with aluminum shield windings. The shield windings carry impressed pulsed currents while eliminating pulsed currents from the dc superconductive windings. Without pulsed currents or pulsed magnetic fields there are no ac losses in standard helium. The major radius of the dipole is 8.85 m; the minor radius is 0.69m; there are 188 turns at 80,000 A and each turn is 4 conductors wound in parallel. The 20,000 A TiNb-copper composite conductor is l0x 1.12 cm in cross section similar to but larger than the FNAL bubble chamber conductor. The shield is 188 turns (equal number of turns is a shielding condition) of hollow aluminum conductor cooled via circulated cold helium gas at 40K. The turns are spaced around the minor circumference according to a cosine distribution which produces zero internal field. In use the shield loss converted to room temperature power is about .8MW when 0.1 MWh is used from a 1

  5. The pulsing CPSD method for subcritical assemblies with pulsed sources

    Ballester, D; Ballester, Daniel; Munoz-Cobo, Jose L.

    2005-01-01

    Stochastic neutron transport theory is applied to the derivation of the two-neutron-detectors cross power spectral density for subcritical assemblies when external pulsed sources are used. A general relationship between the two-detector probability generating functions of the kernel and the source is obtained considering the contribution to detectors statistics of both the pulsed source and the intrinsic neutron source. An expansion in alpha-eigenvalues is derived for the final solution, which permits to take into account the effect of higher harmonics in subcritical systems. Further, expressions corresponding to the fundamental mode approximation are compared with recent results from experiments performed under the MUSE-4 European research project.

  6. High field rf superconductivity: to pulse or not to pulse

    Experimental data on the behavior of superconductors under the application of rf fields of amplitude comparable to their critical fields are sporadic and not always consistent. In many cases the field level at which breakdown in superconducting rf cavities should be expected has not been clearly established. Tests conducted with very short (approx. 1 μs) rf pulses indicate that in this mode of operation fields close to the critical values can be consistently reached in superconducting cavities without breakdown. The advantages and disadvantages of the pulsed method are discussed compared to those of the more standard continuous wave (cw) systems. 60 references

  7. High field RF superconductivity: to pulse or not to pulse

    Experimental data on the behavior of superconductors under the application of RF fields of amplitude comparable to their critical fields are sporadic and not always consistent. In many cases the field level at which breakdown in superconducting RF cavities should be expected has not been clearly established. Tests conducted with very short ( about 1 μs) RF pulses indicate that in this mode of operation fields close to the critical values can be consistently reached in superconducting cavities without breakdown. The advantages and disadvantages of the pulsed method are discussed compared to those of the more standard continuous wave (cw) systems

  8. Pre-earthquake magnetic pulses

    J. Scoville

    2014-12-01

    Full Text Available A semiconductor model of rocks is shown to describe unipolar magnetic pulses, a phenomenon that has been observed prior to earthquakes. These pulses are generated deep in the Earth's crust, in and around the Hypocentral volume, days or even weeks before Earthquakes. They are observable at the surface because their extremely long wavelength allows them to pass through kilometers of rock. Interestingly, the source of these pulses may be triangulated to pinpoint locations where stresses are building deep within the crust. We couple a semiconductor drift-diffusion model to a magnetic field in order to describe the electromagnetic effects associated with electrical currents flowing within rocks. The resulting system of equations is solved numerically and it is seen that a volume of rock may act as a diode that produces transient currents when it switches bias. These unidirectional currents are expected to produce transient unipolar magnetic pulses similar in form, amplitude, and duration to those observed before earthquakes, and this suggests that the pulses could be the result of geophysical semiconductor processes.

  9. Pre-earthquake magnetic pulses

    Scoville, J.; Heraud, J.; Freund, F.

    2015-08-01

    A semiconductor model of rocks is shown to describe unipolar magnetic pulses, a phenomenon that has been observed prior to earthquakes. These pulses are suspected to be generated deep in the Earth's crust, in and around the hypocentral volume, days or even weeks before earthquakes. Their extremely long wavelength allows them to pass through kilometers of rock. Interestingly, when the sources of these pulses are triangulated, the locations coincide with the epicenters of future earthquakes. We couple a drift-diffusion semiconductor model to a magnetic field in order to describe the electromagnetic effects associated with electrical currents flowing within rocks. The resulting system of equations is solved numerically and it is seen that a volume of rock may act as a diode that produces transient currents when it switches bias. These unidirectional currents are expected to produce transient unipolar magnetic pulses similar in form, amplitude, and duration to those observed before earthquakes, and this suggests that the pulses could be the result of geophysical semiconductor processes.

  10. Pulse oximetry in pediatric practice.

    Fouzas, Sotirios; Priftis, Kostas N; Anthracopoulos, Michael B

    2011-10-01

    The introduction of pulse oximetry in clinical practice has allowed for simple, noninvasive, and reasonably accurate estimation of arterial oxygen saturation. Pulse oximetry is routinely used in the emergency department, the pediatric ward, and in pediatric intensive and perioperative care. However, clinically relevant principles and inherent limitations of the method are not always well understood by health care professionals caring for children. The calculation of the percentage of arterial oxyhemoglobin is based on the distinct characteristics of light absorption in the red and infrared spectra by oxygenated versus deoxygenated hemoglobin and takes advantage of the variation in light absorption caused by the pulsatility of arterial blood. Computation of oxygen saturation is achieved with the use of calibration algorithms. Safe use of pulse oximetry requires knowledge of its limitations, which include motion artifacts, poor perfusion at the site of measurement, irregular rhythms, ambient light or electromagnetic interference, skin pigmentation, nail polish, calibration assumptions, probe positioning, time lag in detecting hypoxic events, venous pulsation, intravenous dyes, and presence of abnormal hemoglobin molecules. In this review we describe the physiologic principles and limitations of pulse oximetry, discuss normal values, and highlight its importance in common pediatric diseases, in which the principle mechanism of hypoxemia is ventilation/perfusion mismatch (eg, asthma exacerbation, acute bronchiolitis, pneumonia) versus hypoventilation (eg, laryngotracheitis, vocal cord dysfunction, foreign-body aspiration in the larynx or trachea). Additional technologic advancements in pulse oximetry and its incorporation into evidence-based clinical algorithms will improve the efficiency of the method in daily pediatric practice. PMID:21930554

  11. Pulsed neutron sources at Dubna

    In 1960 the first world repetitively pulsed reactor IBR was put into operation. It was the beginning of the story how fission based pulsed neutron sources at Dubna have survived. The engineers involved have experienced many successes and failures in the course of new sources upgrading to finally come to possess the world's brightest neutron source - IBR-2. The details are being reviewed through the paper. The fission based pulsed neutron sources did not reach their final state as yet- the conceptual views of IBR prospects are being discussed with the goal to double the thermal neutron peak flux (up to 2x1016) and to enhance the cold neutron flux by 10 times (with the present one being as high that of the ISIS cold moderator). (author)

  12. Pulsed liquid microjet for microsurgery

    Fletcher, D. A.; Palanker, D. V.

    2001-03-01

    The precision of soft tissue dissection with pulsed lasers in liquid media is typically limited by collateral damage from vapor bubbles created during energy deposition. We present an alternative technique for creating incisions using a pulsed liquid microjet driven by an electric discharge-induced vapor bubble generated inside a micronozzle. We use this technique to create a pulsed jet 30 μm in diameter with a peak velocity of 90 m/s and total ejected volume on the order of 100 pl. Incision tests on a polyacrylamide gel simulating soft tissue show that the width of the cut is comparable to the diameter of the micronozzle and that collateral damage is significantly less than that produced by a vapor bubble not confined by the nozzle.

  13. Radial flow pulse jet mixer

    VanOsdol, John G.

    2013-06-25

    The disclosure provides a pulse jet mixing vessel for mixing a plurality of solid particles. The pulse jet mixing vessel is comprised of a sludge basin, a flow surface surrounding the sludge basin, and a downcoming flow annulus between the flow surface and an inner shroud. The pulse jet mixing vessel is additionally comprised of an upper vessel pressurization volume in fluid communication with the downcoming flow annulus, and an inner shroud surge volume separated from the downcoming flow annulus by the inner shroud. When the solid particles are resting on the sludge basin and a fluid such as water is atop the particles and extending into the downcoming flow annulus and the inner shroud surge volume, mixing occurs by pressurization of the upper vessel pressurization volume, generating an inward radial flow over the flow surface and an upwash jet at the center of the sludge basin.

  14. Cellular tolerance to pulsed heating

    Simanovski, Dimitrii; Sarkar, M.; Irani, A.; O'Connell-Rodwell, C.; Contag, C.; Schwettman, H. Alan; Palanker, D.

    2005-04-01

    Many laser therapies involve significant heating of tissue with pulses varying from picoseconds to minutes in duration. In some of the applications heating is a primary goal, while in others it is an undesirable side effect. In both cases, if a hyperthermia is involved, the knowledge about the threshold temperature leading to irreversible cellular damage is critically important. We study the dependence of the threshold temperature on duration of the heat exposure in the range of 0.3 ms to 5 seconds. Thin layer of cells cultured in a Petri dish was exposed to a pulsed CO2 laser radiation. Laser beam was focused onto sample providing Gaussian intensity distribution in the focal plane with a beam diameter (2w) 2-10 mm. Surface temperature in the central part of the focal spot (1mm in diameter) was measured by thermal infrared (IR) emission from the sample, recorded with a fast IR detector. For pulses shorter than 1 s the temperature profile across the focal spot was found to closely correspond to the radial distribution of the laser beam intensity, thus allowing for accurate determination of temperature at any given distance from the center of the spot. Immediate cellular damage was assessed using vital staining with the live/dead fluorescent assay. Threshold temperatures were found to vary from 65 °C at 5 s of heating to 160 °C at pulses of 0.3 ms in duration. The shorter end of this range was limited by vaporization, which occurs during the laser pulse and results in mechanical damage to cells. Dependence of the maximal temperature on pulse duration could be approximated by Arrhenius law with activation energy being about 1 eV.

  15. Characteristics of the pumping pulse and the output laser pulse for a Cu/CuCl double pulse laser

    Kushner, M J; Culick, F. E. C.

    1980-01-01

    Characteristics of the pumping discharge pulse and laser pulse in a Cu/CuCl double pulse laser have been measured as a function of time delay, buffer gas pressure, and tube temperature. We have found that for otherwise fixed discharge conditions, pumping rates decrease as these quantities are increased. The shape of the laser pulse as a function of time delay is shown to be dependent on the rate of current rise of the pumping pulse. The length of time required by the pumping pulse to achieve ...

  16. Pulsed gate bias control of GaN HEMTs to improve pulse-to-pulse stability in radar applications

    Delprato, Julien; Delias, Arnaud; Medrel, Pierre; Barataud, Denis; Campovecchio, Michel; Neveux, Guillaume; Martin, Audrey; Bouysse, Philippe; Nebus, Jean-Michel; Tolant, C.; Eudeline, P.

    2015-01-01

    A significant improvement is demonstrated in the measured pulse-to-pulse stability of an S-band 6 W GaN high electron mobility transistor (HEMT) power amplifier by generating an appropriate pulse of the gate bias and thus a warm-up drain current just before each radio-frequency (RF) pulse of a periodic and coherent radar burst. The amplitude and the width of this gate bias pulse preceding each periodic RF pulse of the burst are experimentally varied to investigate the trade-off between the im...

  17. Bomb pulse radiocarbon dating

    Modern forensic science has to deal not only with homicides and other traditional crimes but also with more global threats such as the smuggling of nuclear materials, clandestine production of weapons of mass destruction, stockpiling of illicit drugs by state controlled groups and war crimes. Forensic applications have always benefited from the use of advanced analytical tools that can characterize materials found at crime scenes. In this paper we will discuss the use of accelerator mass spectrometry (AMS) as an ultrasensitive tool for the crime laboratories of the third millennium. An important objective in forensic science is to order past events chronologically by analysing materials associated with criminal actions. Radiocarbon dating is known to the general public for its application to historical and prehistorical investigations. Examples of forensic significance include the assassination of the Inca Atahualpa by Francisco Pizarro in the early 1530s, the possible murder of the Tyrolean Ice Man (Oetzi) 5300 years ago and the analysis of the burial cloths allegedly associated with the crucifixion of Jesus Christ . Recent murders, including those associated with war crimes in the Balkans during the 1990s, can be studied using 14C bomb pulse dating. This method has other forensic applications, including investigation of frauds related to food and wine counterfeiting, dating of opium crops and dating of substances used in biological warfare. AMS extends the applicability of the radiocarbon method, allowing the analysis of 14C in submilligram organic samples. Specific molecular compounds extracted from bones, hair, skin and other carbon bearing substances of forensic significance can now be dated, enhancing the sensitivity and reliability of chronological determinations. AMS can also be used to analyse rare actinide isotopes released into the environment during the clandestine production of nuclear weapons or associated with the smuggling of nuclear materials. In

  18. Pulsed neutron porosity logging system

    An improved pulsed neutron porosity logging system is provided in the present invention. A logging tool provided with a 14 MeV pulsed neutron source, an epithermal neutron detector, and a fast neutron detector is moved through a borehole. Repetitive bursts of neutrons irradiate the earth formations and, during the bursts, the fast neutron population is sampled. During the interval between bursts the epithermal neutron population is sampled along with background gamma radiation due to lingering thermal neutrons. The fast and epithermal neutron population measurements are combined to provide a measurement of formation porosity

  19. Induction linacs and pulsed power

    Progress in electronic power conversion technology is making possible a new class of induction linacs that can operate at extremely high repetition rates. Advances in insulator technology, pulse forming line design and switching may also lead to a new type of high current accelerator with accelerating gradients at least an order of magnitude greater than those attainable today. The evolution of the induction accelerator pulsed power system will be discussed along with some details of these emerging technologies which are at the frontiers of accelerator technology

  20. High-speed pulse techniques

    Coekin, J A

    1975-01-01

    High-Speed Pulse Techniques covers the many aspects of technique in digital electronics and encompass some of the more fundamental factors that apply to all digital systems. The book describes the nature of pulse signals and their deliberate or inadvertent processing in networks, transmission lines and transformers, and then examines the characteristics and transient performance of semiconductor devices and integrated circuits. Some of the problems associated with the assembly of these into viable systems operating at ultra high speed are also looked at. The book examines the transients and w

  1. Neuromuscular disruption with ultrashort electrical pulses

    Pakhomov, Andrei; Kolb, Juergen F.; Joshi, Ravindra P.; Schoenbach, Karl H.; Dayton, Thomas; Comeaux, James; Ashmore, John; Beason, Charles

    2006-05-01

    Experimental studies on single cells have shown that application of pulsed voltages, with submicrosecond pulse duration and an electric field on the order of 10 kV/cm, causes sudden alterations in the intracellular free calcium concentration, followed by immobilization of the cell. In order to examine electrical stimulation and incapacitation with such ultrashort pulses, experiments on anesthetized rats have been performed. The effect of single, 450 nanosecond monopolar pulses have been compared with that of single pulses with multi-microsecond duration (TASER pulses). Two conditions were explored: 1. the ability to elicit a muscle twitch, and, 2. the ability to suppress voluntary movement by using nanosecond pulses. The second condition is relevant for neuromuscular incapacitation. The preliminary results indicate that for stimulation microsecond pulses are advantageous over nanosecond pulses, whereas for incapacitation, the opposite seems to apply. The stimulation effects seem to scale with electrical charge, whereas the disruption effects don't follow a simple scaling law. The increase in intensity (time of incapacitation) for a given pulse duration, is increasing with electrical energy, but is more efficient for nanosecond than for microsecond pulses. This indicates different cellular mechanisms for incapacitation, most likely subcellular processes, which have been shown to become increasingly important when the pulse duration is shortened into the nanosecond range. If further studies can confirm these initial results, consequences of reduced pulse duration are a reduction in weight and volume of the pulse delivery system, and likely, because of the lower required energy for neuromuscular incapacitation, reduced safety risks.

  2. Dynamic Characterization of Fiber Optical Chirped Pulse Amplification for Sub-ps Pulses

    Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Rishøj, Lars Søgaard;

    2013-01-01

    We investigate experimentally the propagation of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers, showing a significant broadening of the pulses from 450 fs up to 720 fs due to dispersion and self-phase modulation.......We investigate experimentally the propagation of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers, showing a significant broadening of the pulses from 450 fs up to 720 fs due to dispersion and self-phase modulation....

  3. Pulse dexamethasone therapy versus pulse methylprednisolone therapy for treatment of Graves′s ophthalmopathy

    Rajeev Philip; Sanjay Saran; Manish Gutch; Pushpaltha Agroyia; Rajiv Tyagi; Keshavkumar Gupta

    2013-01-01

    Pulse methylprednisolone therapy is the recommended therapy for moderate to severe and active ophthalmopathy, but high dose pulse methylprednisolone therapy is marred by the chances of fulminant hepatic failure and the high cost of therapy. Dexamethasone pulse therapy can be considered as an alternative to pulse methylprednisolone therapy. A prospective randomized control trial was carried out in 21 patients comparing pulse dexamethasone therapy versus pulse methyprednisolone therapy in Grave...

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

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

    2005-01-01

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

  5. Control circuit for a pulsed neutron source

    A pulsed neutron source is operated with a control circuit which produces neutron pulses very sharply defined with reference to time. A relatively steep rising high voltage control pulse for the ion source is produced by means of a low voltage input control pulse. Simultaneously, a control pulse is generated for a delayed quenching circuit, which quenches the high voltage control pulse for the ion source after a fixed time delay for a short time. The control voltage obtained for the ion source and for the neutron output is sharply defined as regards time. (orig.)

  6. Nonparametric estimation of ultrasound pulses

    Jensen, Jørgen Arendt; Leeman, Sidney

    1994-01-01

    An algorithm for nonparametric estimation of 1D ultrasound pulses in echo sequences from human tissues is derived. The technique is a variation of the homomorphic filtering technique using the real cepstrum, and the underlying basis of the method is explained. The algorithm exploits a priori...

  7. Pulsed neutron generator for logging

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

  8. Pulsed "three-photon" light

    Gevorgyan, T V

    2012-01-01

    Generating multi-photon entangled states is a primary task for applications of quantum information processing. We investigate production of photon-triplet in a regime of light amplification in second-order nonlinear media under action of a pulsed laser beam. For this goal the process of cascaded three-photon splitting in an optical cavity driven by a sequence of laser pulses with Gaussian time-dependent envelopes is investigated. Considering production of photon-triplet for short-time regime and in the cascaded three-wave collinear configuration Generating multi-photon entangled states is a primary task for applications of quantum information processing. We investigate production of photon-triplet in a regime of light amplification in second-order nonlinear media under action of a pulsed laser beam. For this goal the process of cascaded three-photon splitting in an optical cavity driven by a sequence of laser pulses with Gaussian time-dependent envelopes is investigated. Considering production of photon-tripl...

  9. Ultrashort-pulse laser machining

    Banks, P S; Feit, M D; Nguyen, H T; Perry, M D; Rubenchik, A M; Sefcik, J A; Stuart, B C

    1998-09-01

    A new type of material processing is enabled with ultrashort (t < 10 ps) laser pulses. Cutting, drilling, sculpting of all materials (biologic materials, ceramics, sapphire, silicon carbide, diamond, metals) occurs by new mechanisms that eliminate thermal shock or collateral damage. High-precision machining to submicron tolerances is enabled resulting in high surface quality and negligible heat affected zone.

  10. Ultrashort-pulse lasers machining

    Banks, P S; Feit, M D; Nguyen, H T; Perry, M D, Stuart, B C

    1999-01-22

    A new type of material processing is enabled with ultrashort (t < 10 psec) laser pulses. Cutting, drilling, sculpting of all materials (biologic materials, ceramics, sapphire, silicon carbide, diamond, metals) occurs by new mechanisms which eliminate thermal shock or collateral damage. High precision machining to submicron tolerances is enabled resulting in high surface quality and negligible heat affected zone.

  11. Pulsed laser irradiation of silicon

    Pulsed laser irradiation of silicon was investigated with a ruby laser, having a pulse width of 30 ns and a variable energy up to 1.5 Joules. Peak powers as high as 50 MW are obtained, which is sufficient to cause melting to depths of a few thousand angstroem. In this study, development of heat flow theory made it possible to calculate temperature profiles in silicon during pulsed laser irradiation. Silicon self-diffusion measurements, laser annealing of damage in As implanted silicon, and laser induced doping of single crystal silicon was also investigated. A computer programme was used to calculate the temperature profiles in silicon during pulsed laser irradiation. Radioactive 31Si (half-life = 2.62 hours) was used to determine for the first time the self-diffusion of silicon in silicon during pulsed laser irradiation. Radioactivity profiles in the silicon sample were measured by anodic oxidation, sequential removal of the formed SiO2 by etching in dilute HF and measurement of the radioactivity left in the sample. The removal of damage caused during ion implantation of Si substrates with As was investigated by using laser annealing. Rutherford backscattering of charged nuclear paricles coupled with the channeling technique, showed that an amorphous layer 1140 A thick formed during implantation. Complete removal of this damage only started to take place at energies high enough to cause melting to depths greater than the amorphous/single crystal interface. During resolidification, the molten silicon regrows epitaxially leading to complete removal of all the damage. Disorder removal started at 0.6 Jcm-2, while complete damage removal was achieved at energies above 1.5 Jcm-2. The doping of silicon with Sb, Bi and In by laser assisted diffusion was investigated from evaporated layers as well as solutions of these dopants

  12. Wave equations for pulse propagation

    Theoretical discussions of the propagation of pulses of laser radiation through atomic or molecular vapor rely on a number of traditional approximations for idealizing the radiation and the molecules, and for quantifying their mutual interaction by various equations of propagation (for the radiation) and excitation (for the molecules). In treating short-pulse phenomena it is essential to consider coherent excitation phenomena of the sort that is manifest in Rabi oscillations of atomic or molecular populations. Such processes are not adequately treated by rate equations for excitation nor by rate equations for radiation. As part of a more comprehensive treatment of the coupled equations that describe propagation of short pulses, this memo presents background discussion of the equations that describe the field. This memo discusses the origin, in Maxwell's equations, of the wave equation used in the description of pulse propagation. It notes the separation into lamellar and solenoidal (or longitudinal and transverse) and positive and negative frequency parts. It mentions the possibility of separating the polarization field into linear and nonlinear parts, in order to define a susceptibility or index of refraction and, from these, a phase and group velocity. The memo discusses various ways of characterizing the polarization characteristics of plane waves, that is, of parameterizing a transverse unit vector, such as the Jones vector, the Stokes vector, and the Poincare sphere. It discusses the connection between macroscopically defined quantities, such as the intensity or, more generally, the Stokes parameters, and microscopic field amplitudes. The material presented here is a portion of a more extensive treatment of propagation to be presented separately. The equations presented here have been described in various books and articles. They are collected here as a summary and review of theory needed when treating pulse propagation

  13. Cryosurgery with pulsed electric fields.

    Charlotte S Daniels

    Full Text Available This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused

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

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

  15. Pulse frequency classification based on BP neural network

    WANG Rui; WANG Xu; YANG Dan; FU Rong

    2006-01-01

    In Traditional Chinese Medicine (TCM), it is an important parameter of the clinic disease diagnosis to analysis the pulse frequency. This article accords to pulse eight major essentials to identify pulse type of the pulse frequency classification based on back-propagation neural networks (BPNN). The pulse frequency classification includes slow pulse, moderate pulse, rapid pulse etc. By feature parameter of the pulse frequency analysis research and establish to identify system of pulse frequency features. The pulse signal from detecting system extracts period, frequency etc feature parameter to compare with standard feature value of pulse type. The result shows that identify-rate attains 92.5% above.

  16. Digital Communication Using Chaotic Pulse Generators

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

    1999-01-01

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

  17. Generating photon pulses with an oscillating cavity

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

    1998-01-01

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

  18. Treatment Pulse Application for Magnetic Stimulation

    Sun-Seob Choi

    2011-01-01

    Full Text Available Treatment and diagnosis can be made in difficult areas simply by changing the output pulse form of the magnetic stimulation device. However, there is a limitation in the range of treatments and diagnoses of a conventional sinusoidal stimulation treatment pulse because the intensity, width, and form of the pulse must be changed according to the lesion type. This paper reports a multidischarge method, where the stimulation coils were driven in sequence via multiple switching control. The limitation of the existing simple sinusoidal pulse form could be overcome by changing the intensity, width, and form of the pulse. In this study, a new sequential discharge method was proposed to freely alter the pulse width. The output characteristics of the stimulation treatment pulse were examined according to the trigger signal delay applied to the switch at each stage by applying a range of superposition pulses to the magnetic simulation device, which is widely used in industry and medicine.

  19. Nature of giant pulses in radio pulsars

    Petrova, S A

    2006-01-01

    Formation of giant radio pulses is attributed to propagation effects in the plasma of pulsar magnetosphere. Induced scattering of radio waves by the plasma particles is found to lead to an efficient redistribution of the radio emission in frequency. With the steep spectrum of pulsar radiation, intensity transfer between the widely spaced frequencies may imply significant narrow-band amplification of the radiation. This may give rise to giant pulses. It is demonstrated that the statistics of giant pulse intensities observed can be reproduced if one take into account pulse-to-pulse fluctuations of the plasma number density and the original intensity. Polarization properties of the strongly amplified pulses, their location in the average pulse window and the origin of the nanostructure of giant pulses are discussed as well.

  20. Linear transformer driver for pulse generation

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

    2015-04-07

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

  1. Developing classification indices for Chinese pulse diagnosis

    Shu, Jian-Jun

    2014-01-01

    Aim: To develop classification criteria for Chinese pulse diagnosis and to objectify the ancient diagnostic technique. Methods: Chinese pulse curves are treated as wave signals. Multidimensional variable analysis is performed to provide the best curve fit between the recorded Chinese pulse waveforms and the collective Gamma density functions. Results: Chinese pulses can be recognized quantitatively by the newly-developed four classification indices, that is, the wave length, the relative phase difference, the rate parameter, and the peak ratio. The new quantitative classification not only reduces the dependency of pulse diagnosis on Chinese physician's experience, but also is able to interpret pathological wrist-pulse waveforms more precisely. Conclusions: Traditionally, Chinese physicians use fingertips to feel the wrist-pulses of patients in order to determine their health conditions. The qualitative theory of the Chinese pulse diagnosis is based on the experience of Chinese physicians for thousands of year...

  2. Pulse shaping on the Nova laser system

    Inertial confinement fusion requires temporally shaped pulses to achieve high gain efficiency. Recently, we demonstrated the ability to produce complex temporal pulse shapes at high power at 0.35 microns on the Nova laser system. 2 refs., 2 figs

  3. Exact Solutions to Short Pulse Equation

    FU Zun-Tao; ZHENG Ming-Hua; LIU Shi-Kuo

    2009-01-01

    In this paper, dependent and independent variable transformations are introduced to solve the short pulse equation. It is shown that different kinds of solutions can be obtained to the short pulse equation.

  4. Electromagnetic Pulses at Short-Pulse Laser Facilities

    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.

  5. Chirped Pulse Microwave Spectroscopy in Pulsed Uniform Supersonic Flows

    Abeysekera, Chamara; Oldham, James; Prozument, Kirill; Joalland, Baptiste; Park, Barratt; Field, Robert W.; Sims, Ian; Suits, Arthur; Zack, Lindsay

    2014-06-01

    We present preliminary results describing the development of a new instrument that combines two powerful techniques: Chirped Pulse-Fourier Transform MicroWave (CP-FTMW) spectroscopy and pulsed uniform supersonic flows. It promises a nearly universal detection method that can deliver quantitative isomer, conformer, and vibrational level specific detection, characterization of unstable reaction products and intermediates and perform unique spectroscopic, kinetics and dynamics measurements. We have constructed a new high-power K_a-band, 26-40 GHz, chirped pulse spectrometer with sub-MHz resolution, analogous to the revolutionary CP-FTMW spectroscopic technique developed in the Pate group at University of Virginia. In order to study smaller molecules, the E-band, 60-90 GHz, CP capability was added to our spectrometer. A novel strategy for generating uniform supersonic flow through a Laval nozzle is introduced. High throughput pulsed piezo-valve is used to produce cold (30 K) uniform flow with large volumes of 150 cm^3 and densities of 1014 molecules/cm3 with modest pumping facilities. The uniform flow conditions for a variety of noble gases extend as far as 20 cm from the Laval nozzle and a single compound turbo-molecular pump maintains the operating pressure. Two competing design considerations are critical to the performance of the system: a low temperature flow is needed to maximize the population difference between rotational levels, and high gas number densities are needed to ensure rapid cooling to achieve the uniform flow conditions. At the same time, collision times shorter than the chirp duration will give inaccurate intensities and reduced signal levels due to collisional dephasing of free induction decay. Details of the instrument and future directions and challenges will be discussed.

  6. Pulse to pulse monitoring of the SLD detector

    The SLAC Linear Collider produces bunches of positrons and polarized electrons which collide at 120 hertz inside the SLD detector. A limited amount of information is collected for each pulse in the modules which do real-time data acquisition. Buffers of approximately ten seconds' worth of this monitor data are periodically delivered to a VAX. The generation and uses of the monitor data will be discussed

  7. Methods for High Power EM Pulse Measurement

    Fiala, P.; Drexler, P.

    2006-01-01

    There are some suitable methods for the measurement of ultra-short solitary electromagnetic pulses that can be generated by high power pulsed generators. The measurement methods properties have to correspond to the fact whether we want to measure pulses of voltage, current or free-space electromagnetic wave. The need for specific measurement methods occurred by the development of high power microwave pulse generator. Applicable methods are presented in this paper. The method utilizing Faraday...

  8. High Power Picosecond Laser Pulse Recirculation

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P

    2010-04-12

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering based light sources. We demonstrate up to 36x average power enhancement of frequency doubled sub-millijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

  9. The coherent artifact in modern pulse measurements

    Ratner, Justin; Steinmeyer, Günter; Wong, Tsz Chun; Bartels, Randy; Trebino, Rick

    2012-01-01

    We simulate multi-shot intensity-and-phase measurements of unstable ultrashort-pulse trains using frequency-resolved-optical-gating (FROG) and spectral phase interferometry for direct electric-field reconstruction (SPIDER). Both techniques fail to reveal the pulse structure. FROG yields the average pulse duration and suggests the instability by exhibiting disagreement between measured and retrieved traces. SPIDER under-estimates the average pulse duration but retrieves the correct average pul...

  10. The digitization of photomultiplier pulse shapes

    This paper describes a system under construction for the pulse shape digitization of photomultiplier pulses in the range 20-500 nS FWHM. The system measures a number of pulse parameters from which the shape may be reconstructed for example, the risetime is measured with a resolution of InS. The method will form the basis for digitising pulses from an array of atmospheric Cerenkov detectors to be deployed in 1976. (orig.)

  11. Dynamic pulsing of a MOPA fiber laser

    Romero, Rosa; Guerreiro, Paulo T.; Hendow, Sami T.; Salcedo, José R.

    2011-05-01

    Dynamic Pulsing is demonstrated using a pulsed MOPA fiber laser at 1064nm. The output of the MOPA laser is a pulsed profile consisting of a burst of closely spaced pulses. Tests were performed under several materials with pulse bursts ranging from 10ns to 1μs and operating from 500kHz down to single shot. In particular, percussion drilling in stainless steel is demonstrated showing improvements in quality and speed of the process. These profiles allow high flexibility and optimization of the process addressing the specificity of the end application. Dynamic Pulsing allows the same MOPA fiber laser to be used in diverse materials as well as different processes such us marking, drilling, scribing and engraving. The pulsed fiber laser used in this study is a MOPA-DY by Multiwave Photonics. It is based on a modulated seed laser followed by a series of fiber amplifiers and ending with an optically isolated collimator. This pulsed laser model has an output in such a way that each trigger produces a fast burst of pulses, with a repetition frequency within the burst of the order of tens of MHz. Within the burst it is possible to change the number of pulses, the individual pulse profile, burst pulse period and even to generate non-periodic burst pulse separations. The laser allows full freedom for all these combinations. The study here reported compares the impact of pulse peak power, number of pulses within a burst and the pulse burst period, on process quality (heat affected zone, debris, hole uniformity) and drilling yield.

  12. Ultrashort-pulse lasers and their applications

    A revolution has occurred over the past ten years in our ability to generate, manipulate, and amplify ultrashort pulses. Laser pulses can be as short as a few femtoseconds (few optical cycles) and possess extreme power up to several terawatts. The applications of these pulses are numerous in physics, chemistry, and biology, where they can be used to time resolve ultrafast events. We review in this article the state of the art in short pulse generation and amplification. (author)

  13. Complementarity of long pulse and short pulse spallation sources

    The complementarity of short pulse spallation sources (SPSS) and steady state (CW) reactors is a widely accepted concept. SPSS and long pulse spallation sources (LPSS) are complementary in two ways: a) in their performance in neutron scattering experiments LPSS closely emulate CW reactors. In this respect two facets of the time-of-flight (TOF) monochromator method adequate for LPSS will be discussed: the superiority of the TOF approach to the crystal monochromator method in high resolution powder diffraction, and the novel technique of repetition rate multiplication in TOF spectroscopy, b) LPSS combined with adequate chopper systems can also emulate SPSS in a number of applications. It will be shown that the LPSS method of producing short neutron pulses is more efficient for cold and thermal neutrons (below an energy of about 100 MeV), while SPSS is the more favourable approach for hot, epithermal neutrons, i.e. in the slowing down regime in contrast to the moderated regime. These two aspects of complementarity of LPSS and SPSS lead to the conclusions that for about 75% of the spectrum of neutron scattering experiments as known of today the LPSS approach is the most advantageous one with a feasible neutron intensity exceeding that available at ILL by a factor of about 30, while for the remaining 25% of applications the SPSS technique is superior with a well-known potential of a similar gain over present day performances. (author) 7 figs., 6 refs

  14. A Study of New Pulse Auscultation System

    Ying-Yun Chen

    2015-04-01

    Full Text Available This study presents a new type of pulse auscultation system, which uses a condenser microphone to measure pulse sound waves on the wrist, captures the microphone signal for filtering, amplifies the useful signal and outputs it to an oscilloscope in analog form for waveform display and storage and delivers it to a computer to perform a Fast Fourier Transform (FFT and convert the pulse sound waveform into a heartbeat frequency. Furthermore, it also uses an audio signal amplifier to deliver the pulse sound by speaker. The study observed the principles of Traditional Chinese Medicine’s pulsing techniques, where pulse signals at places called “cun”, “guan” and “chi” of the left hand were measured during lifting (100 g, searching (125 g and pressing (150 g actions. Because the system collects the vibration sound caused by the pulse, the sensor itself is not affected by the applied pressure, unlike current pulse piezoelectric sensing instruments, therefore, under any kind of pulsing pressure, it displays pulse changes and waveforms with the same accuracy. We provide an acquired pulse and waveform signal suitable for Chinese Medicine practitioners’ objective pulse diagnosis, thus providing a scientific basis for this Traditional Chinese Medicine practice. This study also presents a novel circuit design using an active filtering method. An operational amplifier with its differential features eliminates the interference from external signals, including the instant high-frequency noise. In addition, the system has the advantages of simple circuitry, cheap cost and high precision.

  15. Third Harmonic Imaging using a Pulse Inversion

    Rasmussen, Joachim; Du, Yigang; Jensen, Jørgen Arendt

    The pulse inversion (PI) technique can be utilized to separate and enhance harmonic components of a waveform for tissue harmonic imaging. While most ultrasound systems can perform pulse inversion, only few image the 3rd harmonic component. PI pulse subtraction can isolate and enhance the 3rd...

  16. Perceptions of European stakeholders of pulse fishing

    Kraan, M.L.; Trapman, B.K.; Rasenberg, M.M.M.

    2015-01-01

    This research project examines the concerns and questions of European stakeholders about pulse fishing, in order to assess to what extent the knowledge agenda on pulse fishing covers these issues. To get a first impression of the concerns about pulse fishing, and to get an idea of the stakeholders t

  17. A transformer of closely spaced pulsed waveforms

    Niedra, J.

    1970-01-01

    Passive circuit, using diodes, transistors, and magnetic cores, transforms the voltage of repetitive positive or negative pulses. It combines a pulse transformer with switching devices to effect a resonant flux reset and can transform various pulsed waveforms that have a nonzero average value and are relatively cosely spaced in time.

  18. <3> OMEGA pulse-forming network

    1974-01-01

    Adjustement of the 3 W pulse-forming network of the SPS beam dumping system. When charged at 60 kV, this PFN gives 10 kA, 25 ms current pulses, with oscillations, superimposed on the pulse flat top, of an amplitude of +/- 1 Ka.

  19. Design of multi-pulsed electron source

    A multi-pulsed electron source is introduced, including the design and the first experimental results. The multi- pulsed electron source can generate multi-pulsed intense electron beams with energy of 2 to 3 MeV and beam intensity of 2.5 kA. The pulse interval is adjustable from 100 ns to 1000 ns without special step. An inductive adder with multi-pulsed driving source is chosen to generate pulsed vacuum diode voltage and both velvet cathode and large-emission-area thermionic dispenser cathode are adopted to generate multi-pulsed intense electron beams. In order to adopt the two different cathodes, two different diodes with the same interface are adopted. The first experimental results indicate that the source runs stably. The multi-pulsed diode voltage is now up to 2. 7 MV and the beam intensity is more than 1.6 kA both near the anode hole with Faraday cup and near the exit of the source with B-dot. The experimental results also indicate that using velvet as cathode the cathode plasma is inevitable and beam intensities become much bigger from pulse to pulse; when the larger-emission-area thermionic dispenser cathode is used, there is few cathode plasma and beam intensities are almost the same for-m pulse to pulse. (authors)

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

    Yunhui Wang

    2012-06-01

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

  1. Itraconazole pulse therapy in onychomycosis

    Mishra M

    1998-01-01

    Full Text Available A prospective study of 30 clinically and mycologically diagnosed cases of onychomycosis was carried out for a period of twelve months from May 1996 to April 1997. Itraconazole pulse therapy was given for the 1st week followed by 3 week drug-free period, for 1st 3 months for the finger nail cases and 4 monthes for finger nail + toe nail and toe nail cases. Patients were evaluated at baseline, week 4, week 12, week 16, week 24, up to 12 months and assessed as cleared or markedly improved with clinical and mycological success. The result of our study is very much encouraging. It suggests that the use of itraconazole pulse therapy will maintain the continuous treatment efficacy and is cost effective than continuous therapy.

  2. Powerful microsecond voltage pulse generator

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

  3. Pulsed power driven fusion energy

    Pulsed power is a robust and inexpensive technology for obtaining high powers. Considerable progress has been made on developing light ion beams as a means of transporting this power to inertial fusion capsules. However, further progress is hampered by the lack of an adequate ion source. Alternatively, z-pinches can efficiently convert pulsed power into thermal radiation, which can be used to drive an inertial fusion capsule. However, a z-pinch driven fusion explosion will destroy a portion of the transmission line that delivers the electrical power to the z-pinch. They investigate several options for providing standoff for z-pinch driven fusion. Recyclable Transmission Lines (RTLs) appear to be the most promising approach

  4. Pulsed Power Driven Fusion Energy

    SLUTZ,STEPHEN A.

    1999-11-22

    Pulsed power is a robust and inexpensive technology for obtaining high powers. Considerable progress has been made on developing light ion beams as a means of transporting this power to inertial fusion capsules. However, further progress is hampered by the lack of an adequate ion source. Alternatively, z-pinches can efficiently convert pulsed power into thermal radiation, which can be used to drive an inertial fusion capsule. However, a z-pinch driven fusion explosion will destroy a portion of the transmission line that delivers the electrical power to the z-pinch. They investigate several options for providing standoff for z-pinch driven fusion. Recyclable Transmission Lines (RTLs) appear to be the most promising approach.

  5. Pulsed Power Fusion Program update

    The US Department of Energy has supported a substantial research program in Inertial Confinement Fusion (ICF) since the early 1970s. Over the course of the ensuing 25 years, pulsed power energy, efficiency, and relatively low cost of the technology when compared to the mainline ICF approach involving large glass lasers. These compelling advantages of pulsed power, however, have been tempered with the difficulty that has been encountered in concentrating the energy in space and time to create the high energy and power density required to achieve temperatures useful in indirect drive ICF. Since the Beams '96 meeting two years ago, the situation has changed dramatically and extremely high x-ray power (∼290 TW) and energy (∼1.8 MJ) have been produced in fast x-pinch implosions on the Z accelerator. These sources have been utilized to heat hohlraums to >150 eV and have opened the door to important ICF capsule experiments

  6. Pulsed metallic-plasma generators.

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

    1972-01-01

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

  7. Pulse Propagation on close conductors

    Dieckmann, A

    2001-01-01

    The propagation and reflection of arbitrarily shaped pulses on non-dispersive parallel conductors of finite length with user defined cross section is simulated employing the discretized telegraph equation. The geometry of the system of conductors and the presence of dielectric material determine the capacities and inductances that enter the calculation. The values of these parameters are found using an iterative Laplace equation solving procedure and confirmed for certain calculable geometries including the line charge inside a box. The evolving pulses and the resulting crosstalk can be plotted at any instant and - in the Mathematica notebook version of this report - be looked at in an animation. As an example a differential pair of microstrips as used in the ATLAS vertex detector is analysed.

  8. Unsplit bipolar pulse forming line

    Rhodes, Mark A.

    2011-05-24

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

  9. Pulse amplitude modulated chlorophyll fluorometer

    Greenbaum, Elias; Wu, Jie

    2015-12-29

    Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.

  10. Electromagnetic pulses bone healing booster

    Sintea, S. R.; Pomazan, V. M.; Bica, D.; Grebenisan, D.; Bordea, N.

    2015-11-01

    Posttraumatic bone restoration triggered by the need to assist and stimulate compensatory bone growth in periodontal condition. Recent studies state that specific electromagnetic stimulation can boost the bone restoration, reaching up to 30% decrease in recovery time. Based on the existing data on the electromagnetic parameters, a digital electronic device is proposed for intra oral mounting and bone restoration stimulation in periodontal condition. The electrical signal is applied to an inductive mark that will create and impregnate magnetic field in diseased tissue. The device also monitors the status of the electromagnetic field. Controlled wave forms and pulse frequency signal at programmable intervals are obtained with optimized number of components and miniaturized using surface mounting devices (SMD) circuits and surface mounting technology (SMT), with enhanced protection against abnormal current growth, given the intra-oral environment. The system is powered by an autonomous power supply (battery), to limit the problems caused by powering medical equipment from the main power supply. Currently the device is used in clinical testing, in cycles of six up to twelve months. Basic principles for the electrical scheme and algorithms for pulse generation, pulse control, electromagnetic field control and automation of current monitoring are presented, together with the friendly user interface, suitable for medical data and patient monitoring.

  11. Portable pulse height analyzing system

    Low power, battery operated, compact Portable Pulse Height Analyzing System/Multi Channel Analyzer (PMCA) has been designed and developed for monitoring the various low activity radioisotopes in situ. PMCA can also be used in mobile radiation monitoring vans, wherein, gamma spectrum data collected at different locations can be stored in the battery backed RAM disk and down-loaded on to the PC via a serial link. Designed primarily for measurement and analysis of isotope activity and for field experiments, it can be used with most of the radiation detectors used for pulse height spectrum analysis. PMCA is built around embedded PC hardware architecture wherein all the cards are made with state of the art technology with extensive use of SMT and ASICS. PMCA provides features comparable with standard laboratory models and enables computation of integral area, background area, net peak area, FWHM, peak centroid and energy calibration in the field. This paper describes Portable Pulse Height Analyzing System with focus on following features: a) Hardware implementation of well-known multi channel analyzer technique using embedded PC hardware architecture. b) Software implementation of spectrum acquisition and analysis using high level language namely, C. (author)

  12. Pulse front adaptive optics in multiphoton microscopy

    Sun, B.; Salter, P. S.; Booth, M. J.

    2016-03-01

    The accurate focusing of ultrashort laser pulses is extremely important in multiphoton microscopy. Using adaptive optics to manipulate the incident ultrafast beam in either the spectral or spatial domain can introduce significant benefits when imaging. Here we introduce pulse front adaptive optics: manipulating an ultrashort pulse in both the spatial and temporal domains. A deformable mirror and a spatial light modulator are operated in concert to modify contours of constant intensity in space and time within an ultrashort pulse. Through adaptive control of the pulse front, we demonstrate an enhancement in the measured fluorescence from a two photon microscope.

  13. Method for Generating a Compressed Optical Pulse

    2015-01-01

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

  14. Optimization studies on pulse ionization chambers

    The results are presented of optimization studies on two models of an air-filled, pulse, ionization chamber intended for detecting air impurities. Studies were conducted on the effect of dosage grids, procedure of controlling them, field configuration, type of radioactive source, surface of collecting electrode, and length of dosage pulse. The most critical parameters that have an effect upon the pulse shape, i.t. upon the pulse-amplitude and -length are: procedure of controlling the dosage grid, dosage dosage-pulse length and electric-field intensity. (author)

  15. Custom pulse generator for RPC testing

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

  16. Ion Acceleration by Short Chirped Laser Pulses

    Li, Jian-Xing; Keitel, Christoph H; Harman, Zoltán

    2015-01-01

    Direct laser acceleration of ions by short frequency-chirped laser pulses is investigated theoretically. We demonstrate that intense beams of ions with a kinetic energy broadening of about 1 % can be generated. The chirping of the laser pulse allows the particles to gain kinetic energies of hundreds of MeVs, which is required for hadron cancer therapy, from pulses of energies of the order of 100 J. It is shown that few-cycle chirped pulses can accelerate ions more efficiently than long ones, i.e. higher ion kinetic energies are reached with the same amount of total electromagnetic pulse energy.

  17. New Assessment Model of Pulse Depth Based on Sensor Displacement in Pulse Diagnostic Devices

    Jang-Han Bae; Young Ju Jeon; Jong Yeol Kim; Kim, Jaeuk U.

    2013-01-01

    An accurate assessment of the pulse depth in pulse diagnosis is vital to determine the floating and sunken pulse qualities (PQs), which are two of the four most basic PQs. In this work, we proposed a novel model of assessing the pulse depth based on sensor displacement (SD) normal to the skin surface and compared this model with two previous models which assessed the pulse depth using contact pressure (CP). In contrast to conventional stepwise CP variation tonometry, we applied a continuously...

  18. Production of Picosecond, Kilojoule, and Petawatt Laser Pulses via Raman Amplification of Nanosecond Pulses

    Trines, R. M. G. M.; Fiúza, F.; Bingham, R.; Fonseca, R. A.; Silva, L. O.; Cairns, R. A.; Norreys, P. A.

    2011-01-01

    Raman amplification in plasma has been promoted as a means of compressing picosecond optical laser pulses to femtosecond duration to explore the intensity frontier. Here we show for the first time that it can be used, with equal success, to compress laser pulses from nanosecond to picosecond duration. Simulations show up to 60% energy transfer from pump pulse to probe pulse, implying that multikilojoule ultraviolet petawatt laser pulses can be produced using this scheme. This has important co...

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

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

  20. Control of high power pulse extracted from the maximally compressed pulse in a nonlinear optical fiber

    Yang, Guangye; Lu LI; Jia, Suotang; Mihalache, Dumitru

    2013-01-01

    We address the possibility to control high power pulses extracted from the maximally compressed pulse in a nonlinear optical fiber by adjusting the initial excitation parameters. The numerical results show that the power, location and splitting order number of the maximally compressed pulse and the transmission features of high power pulses extracted from the maximally compressed pulse can be manipulated through adjusting the modulation amplitude, width, and phase of the initial Gaussian-type...

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

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

  2. Pulse detonation engines and components thereof

    Tangirala, Venkat Eswarlu (Inventor); Rasheed, Adam (Inventor); Vandervort, Christian Lee (Inventor); Dean, Anthony John (Inventor)

    2009-01-01

    A pulse detonation engine comprises a primary air inlet; a primary air plenum located in fluid communication with the primary air inlet; a secondary air inlet; a secondary air plenum located in fluid communication with the secondary air inlet, wherein the secondary air plenum is substantially isolated from the primary air plenum; a pulse detonation combustor comprising a pulse detonation chamber, wherein the pulse detonation chamber is located downstream of and in fluid communication with the primary air plenum; a coaxial liner surrounding the pulse detonation combustor defining a cooling plenum, wherein the cooling plenum is in fluid communication with the secondary air plenum; an axial turbine assembly located downstream of and in fluid communication with the pulse detonation combustor and the cooling plenum; and a housing encasing the primary air plenum, the secondary air plenum, the pulse detonation combustor, the coaxial liner, and the axial turbine assembly.

  3. Attosecond pulse shaping using partial phase matching

    We propose a method for programmable shaping of the amplitude and phase of the extreme ultraviolet and x-ray attosecond pulses produced by high-order harmonic generation. It overcomes the bandwidth limitations of existing spectral filters and enables removal of the intrinsic attosecond chirp as well as the synthesis of pulse sequences. It is based on partial phase matching using a longitudinally addressable modulation. Although the method is in principle applicable to any form of partial phase matching, we focus on quasi-phase matching using a counterpropagating pulse train. We present simulations of the production of isolated attosecond pulses at 250 eV, including a 31 as transform-limited pulse, tunably chirped pulses and double pulses. (paper)

  4. Degradation Parameters from Pulse-Chase Experiments

    Sin, Celine; Chiarugi, Davide; Valleriani, Angelo

    2016-01-01

    Pulse-chase experiments are often used to study the degradation of macromolecules such as proteins or mRNA. Considerations for the choice of pulse length include the toxicity of the pulse to the cell and maximization of labeling. In the general case of non-exponential decay, varying the length of the pulse results in decay patterns that look different. Analysis of these patterns without consideration to pulse length would yield incorrect degradation parameters. Here we propose a method that constructively includes pulse length in the analysis of decay patterns and extracts the parameters of the underlying degradation process. We also show how to extract decay parameters reliably from measurements taken during the pulse phase. PMID:27182698

  5. Plasma response to transient high voltage pulses

    S Kar; S Mukherjee

    2013-07-01

    This review reports on plasma response to transient high voltage pulses in a low pressure unmagnetized plasma. Mainly, the experiments are reviewed, when a disc electrode (metallic and dielectric) is biased pulsed negative or positive. The main aim is to review the electron loss in plasmas and particle balance during the negative pulse electrode biasing, when the applied pulse width is less than the ion plasma period. Though the applied pulse width is less than the ion plasma period, ion rarefaction waves are excited. The solitary electron holes are reviewed for positive pulsed bias to the electrode. Also the excitation of waves (solitary electron and ion holes) is reviewed for a metallic electrode covered by a dielectric material. The wave excitation during and after the pulse withdrawal, excitation and propagation characteristics of various electrostatic plasma waves are reviewed here.

  6. Generation of short and intense attosecond pulses

    Khan, Sabih Ud Din

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

  7. Method for pulse to pulse dose reproducibility applied to electron linear accelerators

    An original method for obtaining programmed beam single shots and pulse trains with programmed pulse number, pulse repetition frequency, pulse duration and pulse dose is presented. It is particularly useful for automatic control of absorbed dose rate level, irradiation process control as well as in pulse radiolysis studies, single pulse dose measurement or for research experiments where pulse-to-pulse dose reproducibility is required. This method is applied to the electron linear accelerators, ALIN-10 of 6.23 MeV and 82 W and ALID-7, of 5.5 MeV and 670 W, built in NILPRP. In order to implement this method, the accelerator triggering system (ATS) consists of two branches: the gun branch and the magnetron branch. ATS, which synchronizes all the system units, delivers trigger pulses at a programmed repetition rate (up to 250 pulses/s) to the gun (80 kV, 10 A and 4 ms) and magnetron (45 kV, 100 A, and 4 ms).The accelerated electron beam existence is determined by the electron gun and magnetron pulses overlapping. The method consists in controlling the overlapping of pulses in order to deliver the beam in the desired sequence. This control is implemented by a discrete pulse position modulation of gun and/or magnetron pulses. The instabilities of the gun and magnetron transient regimes are avoided by operating the accelerator with no accelerated beam for a certain time. At the operator 'beam start' command, the ATS controls electron gun and magnetron pulses overlapping and the linac beam is generated. The pulse-to-pulse absorbed dose variation is thus considerably reduced. Programmed absorbed dose, irradiation time, beam pulse number or other external events may interrupt the coincidence between the gun and magnetron pulses. Slow absorbed dose variation is compensated by the control of the pulse duration and repetition frequency. Two methods are reported in the electron linear accelerators' development for obtaining the pulse to pulse dose reproducibility: the method

  8. Pulsed plasma etching for semiconductor manufacturing

    Power-modulated (pulsed) plasmas have demonstrated several advantages compared to continuous wave (CW) plasmas. Specifically, pulsed plasmas can result in a higher etching rate, better uniformity, and less structural, electrical or radiation (e.g. vacuum ultraviolet) damage. Pulsed plasmas can also ameliorate unwanted artefacts in etched micro-features such as notching, bowing, micro-trenching and aspect ratio dependent etching. As such, pulsed plasmas may be indispensable in etching of the next generation of micro-devices with a characteristic feature size in the sub-10 nm regime. This work provides an overview of principles and applications of pulsed plasmas in both electropositive (e.g. argon) and electronegative (e.g. chlorine) gases. The effect of pulsing the plasma source power (source pulsing), the electrode bias power (bias pulsing), or both source and bias power (synchronous pulsing), on the time evolution of species densities, electron energy distribution function and ion energy and angular distributions on the substrate is discussed. The resulting pulsed plasma process output (etching rate, uniformity, damage, etc) is compared, whenever possible, to that of CW plasma, under otherwise the same or similar conditions. (topical review)

  9. CFD simulation of pulse combustion's performance

    Rahmatika, Annie Mufyda; Widiyastuti, W.; Winardi, Sugeng; Nurtono, Tantular; Machmudah, Siti; Kusdianto, Joni, I. Made

    2016-02-01

    This study aims to show changes in the performance of combustion using pulse combustion at specified intervals using simulation. Simulations is performed using Computational Fluid Dynamics analysis (CFD) software Ansys Fluent 15.0. Analysis used 2D illustration axisymmetric with k-ɛ turbulence models. Propane was selected as fuel at a flow rate of 15 L/min. Air with flow rate of 375 L/min is used as oxidizer. To investigate the advantages of using pulse combustion, the simulated pulse combustion is compared to normal combustion without a pulse. This is done by displaying descriptions of the phenomenon, mechanisms and results output gas combustor. From the analysis of simulation results showed that in 1 minute burning time, burning fuel without requiring pulse as much as 15 L while the pulse combustion requires half of the fuel which is 12.5 L. However, the higher average of temperature was generated by pulse combustion and the amounts of unburned fuel that comes out of the combustor less than without the use of pulse combustion. So, it can be concluded that the pulse combustion is more efficient than combustion without a pulse.

  10. Atomic collisions involving pulsed positrons

    Merrison, J. P.; Bluhme, H.; Field, D.;

    2000-01-01

    Conventional slow positron beams have been widely and profitably used to study atomic collisions and have been instrumental in understanding the dynamics of ionization. The next generation of positron atomic collision studies are possible with the use of charged particle traps. Not only can large...... instantaneous intensities be achieved with in-beam accumulation, but more importantly many orders of magnitude improvement in energy and spatial resolution can be achieved using positron cooling. Atomic collisions can be studied on a new energy scale with unprecedented precion and control. The use of...... accelerators for producing intense positron pulses will be discussed in the context of atomic physics experiments....

  11. Lamb pulse observed in nature

    Kanamori, Hiroo; Given, Jeffrey W.

    1983-01-01

    Seismograms observed at Longmire, Washington, for four eruptions of Mt. St. Helens (May 18, June 13, August 7, and August 8, 1980), can be interpreted as Lamb pulses excited by a nearly vertical single force that represents the counter force of the eruption. These data provide reliable estimates of the impulse of the force K (time integral of the force) from which the total momentum and the kinetic energy, E, of the ejecta associated with the eruption can be estimated. The values of K are est...

  12. High-Precision Pulse Generator

    Katz, Richard; Kleyner, Igor

    2011-01-01

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

  13. High-power pulsed lasers

    The ideas that led to the successful construction and operation of large multibeam fusion lasers at the Lawrence Livermore Laboratory are reviewed. These lasers are based on the use of Nd:glass laser materials. However, most of the concepts are applicable to any laser being designed for fusion experimentation. This report is a summary of lectures given by the author at the 20th Scottish University Summer School in Physics, on Laser Plasma Interaction. This report includes basic concepts of the laser plasma system, a discussion of lasers that are useful for short-pulse, high-power operation, laser design constraints, optical diagnostics, and system organization

  14. Electromagnetic pulse from nuclear explosions

    The effect of the electromagnetic pulse (EMP) accompanying a nuclear explosion on electronic equipment is presented largely in the form of examples of damage to equipment during nuclear test explosions. The range of such effects is related to the height above the ground at which the explosion takes place. Electric fields and currents generated by EMP in a number of tests, as measured or estimated at various distances are cited. Underground explosions only give EMP over short distances, less than 30 km, while the EMP from conventional explosions is weak and has no significance for electronic equipment. (JIW)

  15. Pulse oximetry for perioperative monitoring

    Pedersen, Tom; Nicholson, Amanda; Hovhannisyan, Karen;

    2014-01-01

    on the methods used for randomization and allocation concealment. It was impossible for study personnel to be blinded to participant allocation in the study, as they needed to be able to respond to oximetry readings. Appropriate steps were taken to minimize detection bias for hypoxaemia and complication outcomes...... to improved reliable outcomes, effectiveness and efficiency. Routine continuous pulse oximetry monitoring did not reduce transfer to the ICU and did not decrease mortality, and it is unclear whether any real benefit was derived from the application of this technology for patients recovering from...

  16. Ternary Chaotic Pulse Compression Sequences

    J. B. Seventline

    2010-09-01

    Full Text Available In this paper method available for generating ternary sequences is discussed. These sequences are useful in many applications but specifically in synchronization of block codes and pulse compression in radar. The ternary sequences are derived from chaotic maps. It is feasible to achieve simultaneously superior performances in detection range and range resolution using the proposed ternary sequences. The properties of these sequences like autocorrelation function, Peak Side Lobe Ratio (PSLR, ambiguity diagram and performance under AWGN noise background has been studied. The generation of these sequences is much simpler, and the available number of sequences is virtually infinite and not limited by the length of the sequence.

  17. Repetitively pulsed material testing facility

    A continuously operated, 1 pps, dense-plasma-focus device capable of delivering a minimum of 1015 neutrons per pulse for material testing purposes is described. Moderate scaling from existing results is sufficient to provide 2 x 1013 n/cm2.s to a suitable target. The average power consumption, which has become a major issue as a result of the energy crisis, is analyzed with respect to other plasma devices and is shown to be highly favorable. A novel approach to the capacitor bank and switch design allowing repetitive operation is discussed. (U.S.)

  18. Research and development of ns pulse width ultrafast pulsed power supply

    High repetition rate, nanosecond pulse width fast pulsed power supply is a key technology to be overcome for particle accelerator fast kicker injection and ejection. In this paper, inductive adder topology, the RF MOSFET and its driver circuit were studied by computer simulation and table circuit experiment. On the basis of theory research, a ten-grade inductive adder pulsed power supply evaluating prototype was developed. The preliminary test of the prototype was completed. A ten-grade adder can produce a short pulse of pulse amplitude >4.3 kV, front edge <2.8 ns, and pulse width <9 ns into 50 Ω at 500 Hz repetition rate. (authors)

  19. Interactions between butterfly-shaped pulses in the inhomogeneous media

    Pulse interactions affect pulse qualities during the propagation. Interactions between butterfly-shaped pulses are investigated to improve pulse qualities in the inhomogeneous media. In order to describe the interactions between butterfly-shaped pulses, analytic two-soliton solutions are derived. Based on those solutions, influences of corresponding parameters on pulse interactions are discussed. Methods to control the pulse interactions are suggested. - Highlights: • Interactions between butterfly-shaped pulses are investigated. • Methods to control the pulse interactions are suggested. • Analytic two-soliton solutions for butterfly-shaped pulses are derived

  20. A versatile programmable CAMAC random pulse generator

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

  1. Ionization of atoms by chirped attosecond pulses

    We investigate the ionization dynamics of atoms by chirped attosecond pulses using the strong field approximation method. The pulse parameters are carefully chosen in the regime where the strong field approximation method is valid. We analyse the effects of the chirp of attosecond pulses on the energy distributions and the corresponding left-right asymmetry of the ionized electrons. For a single chirped attosecond pulse, the ionized electrons can be redistributed and the left-right asymmetry shows oscillations because of the introduction of the chirp. For time-delayed double attosecond pulses at different intensities with the weaker one chirped, exchanging the order of the two pulses shows a relative shift of the energy spectra, which can be explained by the different effective time delays of different frequency components because of the chirp. (atomic and molecular physics)

  2. Chirped pulse amplification: Present and future

    Short pulses with ultrahigh peak powers have been generated in Nd: glass and Alexandrite using the Chirped Pulse Amplification (CPA) technique. This technique has been successful in producing picosecond terawatt pulses with a table-top laser system. In the near future, CPA will be applied to large laser systems such as NOVA to produce petawatt pulses (1 kJ in a 1 ps pulse) with focused intensities exceeding 10/sup /plus/21/ W/cm2. These pulses will be associated with electric fields in excess of 100 e/a/sub o/2 and blackbody energy densities equivalent to 3 /times/ 1010 J/cm3. This petawatt source will have important applications in x-ray laser research and will lead to fundamentally new experiments in atomic, nuclear, solid-state, plasma, and high-energy density physics. A review of present and future designs are discussed. 17 refs., 5 figs

  3. Design of pulse deflection magnet

    Deflection magnets are used for the purposes of deflecting the orbit and analyzing the momentum of charged particles, switching charged particles by a pulsed magnetic field and others, in experimental apparatuses or particle accelerators. Here only the fundamental analysis and calculation of the characteristics of the deflection magnets being used in the National Laboratory for High Energy Physics are described. First, the magnetic field intensity B required to bend the path of charged particles, and next, the exciting current required are determined. The effect of a magnetic field when charged particles pass by depends on the effective magnet pole length. Cooling of the magnets is performed by passing cooling water through the hollow conductors used for the magnet coils. The yoke of a pulse magnet is made of silicon steel sheets, the purposes of which are to gain high permeability and reduce eddy current, but the skin effect is also to be considered. Then the inductance of the magnets is determined. Heat generation due to the eddy current in a beam duct in magnet gap must be also calculated. In the practical use of this magnet, beam can be deflected nearly as calculated. A stainless steel beam duct is enough to be used for a few Hz repetition though considerable heat is generated due to eddy current. The beam duct will be replaced with a ceramic duct in future. (Wakatsuki, Y.)

  4. Interpretation of Pulsed Source Experiments

    Pulsed neutron experiments performed during reactor commissioning programmes constitute important examples in which non-separable transients play an important role. Subcritical states studied with partial core loadings ate generally highly reflected, for example, and suffer gross flux distortions upon insertion of control rods. We have developed methods for theoretically simulating the response of non-uniform reactors to pulsed sources and have applied these to a wide range of typical experimental conditions anticipated during the commissioning programme of the Experimental Gas-Cooled Reactor (EGCR). The space-dependent kinetics equations, are solved for two to six neutron groups and one to six delayed neutron precursors by a semi-analytical method which is based entirely on the application of matrix techniques. Two classes of experiments have been examined, involving respectively the prompt transient and the total transient. In the first class we consider the common prompt decay experiment and the (β/Λ) technique, and in the second the source-jerk experiment. Theoretical simulations of these have been used to study the effects of higher modes and other factors affecting their interpretation. We have found that space-dependent effects are greatly suppressed in many important cases in experiments performed with 14-MeV source neutrons. Furthermore, for the source-jerk experiments, a relationship has been derived involving the volume integration of experimental measurements which provides an exact expression for the reactivity including the effects of all modes. (author)

  5. Pulsed UV and VUV excilamps

    Tarasenko, Victor F.; Erofeev, Mikhail V.; Kostyrja, Igor D.; Lomaev, Mikhail I.; Rybka, Dmitri V.

    2008-05-01

    Emission characteristics of a nanosecond discharge in nitrogen, inert gases and its halogenides without preionization of the gap from an auxiliary source have been investigated. A volume discharge, initiated by an avalanche electron beam (VDIAEB) was realized at pressures up to 12 atm. It has been shown that at VDIAEB excitation no less than 90% energy in the 120-850 nm range is emitted by Xe, Kr, Ar dimers. Xenon spectra in the range 120-850 nm and time-amplitude characteristics have been recorded and analyzed for various excitation regimes. In xenon at pressure of 1.2 atm, the energy of spontaneous radiation in the full solid angle was ~ 45 mJ/cm3, and the FWHM of a radiation pulse was ~ 110 ns. The spontaneous radiation power rise in xenon was observed at pressures up to 12 atm. Pulsed power densities of radiation of inert gases halogenides excited by VDIAEB was ~ 4.5 kW/cm2 at efficiency up to 5.5 %.

  6. Pulse waveform analysis as a bridge between pulse examination in Chinese medicine and cardiology.

    de Sá Ferreira, Arthur; Lopes, Agnaldo José

    2013-04-01

    Pulse examination was probably the earliest attempt to distinguish between health and illnesses. Starting at the pre-Hippocratic era, Chinese medicine practitioners developed techniques for pulse examination and defined pulse images based on their perceptions of pulse waveforms at the radial artery. Pulse images were described using basic variables (frequency, rhythm, wideness, length, deepness, and qualities) developed under philosophical trends such as Taoism and Confucianism. Recent advances in biomedical instrumentation applied to cardiology opened possibilities to research on pulse examination based on ancient Chinese medical theories: the pulse wave analysis. Although strongly influenced by philosophy, some characteristics used to describe a pulse image are interpretable as parameters obtained by pulse waveform analysis such as pulse wave velocity and augmentation index. Those clinical parameters reflect concepts unique to Chinese medicine - such as yinyang - while are based on wave reflection and resonance theories of fluids mechanics. Major limitations for integration of Chinese and Western pulse examination are related to quantitative description of pulse images and pattern differentiation based on pulse examination. Recent evidence suggests that wave reflection and resonance phenomena may bridge Chinese medicine and cardiology to provide a more evidence-based medical practice. PMID:23546634

  7. Comparative study on pulsed arc discharge and pulsed corona like discharge in water

    Huang, Y.; Yan, H.; Zhang, Z.; Li, S.; Yan, K. [Zhejiang Univ., Hangzhou (China). Industrial Ecology and Environment Research Inst.

    2010-07-01

    Electric discharge in water generates intense UV radiation, shockwaves, and active radicals. The technology of pulsed discharge in water has broad applications in marine services, medical treatment and environmental pollution control. This study compared pulsed arc discharge and pulsed corona like discharge using a homemade all solid-state pulsed power system. Voltage and current waveforms, light emission and shockwave strength were detected simultaneously to calculate energy partition of both kinds of pulsed discharge. The differences in current, light emission and shockwave strength were presented. The study showed that energy injection into plasma of pulsed arc discharge varies with the breakdown time, while pulsed corona like discharge has a stable energy injection. A time lag between the application of voltage and breakdown was observed in both pulsed arc discharge and pulsed corona like discharge. The peak current and the light emission of the pulsed arc discharge was much bigger than the pulsed corona discharge, but the difference of shockwave strength was not as obvious. It was concluded that the pulsed arc discharge is more suitable for treating waste water and disinfecting drinking water because of its stronger UV light emission. In marine service, pulsed corona like discharge is more suitable because of its comparative shockwave strength and its stable discharge process. 11 refs., 1 tab., 7 figs.

  8. Pulsed TRIGA reactor as substitute for long pulse spallation neutron source

    TRIGA reactor cores have been used to demonstrate various pulsing applications. The TRIGA reactor fuel (U-ZrHx) is very robust especially in pulsing applications. The features required to produce 50 pulses per second have been successfully demonstrated individually, including pulse tests with small diameter fuel rods. A partially optimized core has been evaluated for pulses at 50 Hz with peak pulsed power up to 100 MW and an average power up to 10 MW. Depending on the design, the full width at half power of the individual pulses can range between 2000 μsec to 3000 μsec. Until recently, the relatively long pulses (2000 μsec to 3000 μsec) from a pulsed thermal reactor or a long pulse spallation source (LPSS) have been considered unsuitable for time-of-flight measurements of neutron scattering. More recently considerable attention has been devoted to evaluating the performance of long pulse (1000 to 4000 μs) spallation sources for the same type of neutron measurements originally performed only with short pulses from spallation sources (SPSS). Adequate information is available to permit meaningful comparisons between CW, SPSS, and LPSS neutron sources. Except where extremely high resolution is required (fraction of a percent), which does require short pulses, it is demonstrated that the LPSS source with a 1000 msec or longer pulse length and a repetition rate of 50 to 60 Hz gives results comparable to those from the 60 MW ILL (CW) source. For many of these applications the shorter pulse is not necessarily a disadvantage, but it is not an advantage over the long pulse system. In one study, the conclusion is that a 5 MW 2000 μsec LPSS source improves the capability for structural biology studies of macromolecules by at least a factor of 5 over that achievable with a high flux reactor. Recent studies have identified the advantages and usefulness of long pulse neutron sources. It is evident that the multiple pulse TRIGA reactor can produce pulses comparable to those

  9. Stretched pulse Yb3+:silica fibre laser

    Cautaerts, V.; Richardson, D.J.; Paschotta, R.; Hanna, D.C.

    1997-01-01

    We report what we believe to be the first results on short-pulse generation in Yb3+:silica fiber. By applying the stretched pulse technique in a unidirectional, polarization-switch Yb3+ fiber laser incorporating a prism-based dispersive delay line, we obtain self-start mode locking and 100pJ pulses that can be compressed to give clean chirp-free

  10. Pulse Shaped OFDM for 5G Systems

    Zhao, Zhao; Schellmann, Malte; Gong, Xitao; Wang, Qi; Böhnke, Ronald; Guo, Yan

    2016-01-01

    OFDM-based waveforms with filtering or windowing functionalities are considered key enablers for a flexible air-interface design for multi-service support in future 5G systems. One candidate from this category of waveforms is pulse shaped OFDM, which follows the idea of subcarrier filtering and aims at fully maintaining the advantages of standard OFDM systems while addressing their drawbacks. In this paper, we elaborate on several pulse shaping design methods, and show how pulse shapes can be...

  11. Investigation of pulsed voltage limiters characteristics

    Karimov A. V.

    2012-06-01

    Full Text Available A new method for measuring the voltage limit is offered. It has been designed to measure high-power pulsed current of voltage limiters. The error of this method is half as much as the error of the known method of direct measurement. The investigation of dependence of power capability of single-crystal and double-crystal voltage limiters and of the pulsed operation time on pulse duration.

  12. Investigation of pulsed voltage limiters characteristics

    Karimov A. V.; Yodgorova D. M.; Rakhmatov A. Z.; Skornyakov S. L.; Petrov D. A.; Abdulkhayev O. A.

    2012-01-01

    A new method for measuring the voltage limit is offered. It has been designed to measure high-power pulsed current of voltage limiters. The error of this method is half as much as the error of the known method of direct measurement. The investigation of dependence of power capability of single-crystal and double-crystal voltage limiters and of the pulsed operation time on pulse duration.

  13. Encoding and decoding of femtosecond pulses.

    Weiner, A M; Heritage, J P; Salehi, J A

    1988-04-01

    We demonstrate the spreading of femtosecond optical pulses into picosecond-duration pseudonoise bursts. Spreading is accomplished by encoding pseudorandom binary phase codes onto the optical frequency spectrum. Subsequent decoding of the spectral phases restores the original pulse. We propose that frequency-domain encoding and decoding of coherent ultrashort pulses could form the basis for a rapidly reconfigurable, code-division multiple-access optical telecommunications network. PMID:19745879

  14. PULSE DRYING EXPERIMENT AND BURNER CONSTRUCTION

    Robert States

    2006-07-15

    Non steady impingement heat transfer is measured. Impingement heating consumes 130 T-BTU/Yr in paper drying, but is only 25% thermally efficient. Pulse impingement is experimentally shown to enhance heat transfer by 2.8, and may deliver thermal efficiencies near 85%. Experimental results uncovered heat transfer deviations from steady theory and from previous investigators, indicating the need for further study and a better theoretical framework. The pulse burner is described, and its roll in pulse impingement is analyzed.

  15. Characteristics of pulsed discharge plasma in water

    Namihira, Takao; Yamaguchi, Takahiro; Yamamoto, Kunihiro; Jaegu, Choi; Kiyan, Tsuyoshi; Sakugawa, Takashi; Katsuki, Sunao; Akiyama, Hidenori; ナミヒラ, タカオ; ヤマグチ, タカヒロ; ヤマモト, クニヒロ; ジェグ, チョイ; キヤン, ツヨシ; サクガワ, タカシ; カツキ, スナオ

    2005-01-01

    Recently, pulsed discharge plasma produced underwater has been an attractive method to treat wasted water. It is well known that pulsed discharge in water has some physical effects, such as an intense electric field at a tip of discharge plasma, an ultra violet radiation, a chemically radical formation and shockwave generation, for cleaning water. However, the physical characteristics of the pulsed discharge plasma induced underwater are still unclear. For the optimization of the water treatm...

  16. New pulse modulator with low switching frequency

    Golub V. S.

    2014-01-01

    The author presents an integrating pulse modulator (analog signal converter) with the pulse frequency and duration modulation similar to sigma-delta modulation (with low switching frequency), without quantization. The modulator is characterized by the absence of the quantization noise inherent in sigma-delta modulator, and a low switching frequency, unlike the pulse-frequency modulator. The modulator is recommended, in particular, to convert signals at the input of the class D power amplifier.

  17. Filters for High Rate Pulse Processing

    Alpert, B. K.; Horansky, R. D.; Bennett, D.A.; Doriese, W. B.; Fowler, J. W.; Hoover, A. S.; Rabin, M. W.; Ullom, J. N.

    2012-01-01

    We introduce a filter-construction method for pulse processing that differs in two respects from that in standard optimal filtering, in which the average pulse shape and noise-power spectral density are combined to create a convolution filter for estimating pulse heights. First, the proposed filters are computed in the time domain, to avoid periodicity artifacts of the discrete Fourier transform, and second, orthogonality constraints are imposed on the filters, to reduce the filtering procedu...

  18. Wideband transmitter for pulse NMR spectrometer

    A wideband pulse transmitter for NMR excitation in fields of up to 2.4 T (except for 1H, 1F, 203Tl, and 205Tl nuclei) is described. The transmitter provides a pulse power of 400-600 W into a 50-Omega load at frequencies of 2-40 MHz. The transmitter is equipped with a pulse programmer, which allows independent setting, in each of 16 program steps, of pulse durations or pauses of from 10-7 to 103 sec, output powers of from 0 to -63 dB, and a phase of radio-frequency filling of 0 or 1800

  19. Three pulse recoupling and phase jump matching

    Lin, James; Griffin, R. G.; Nielsen, Niels Chr.; Khaneja, Navin

    2016-02-01

    The paper describes a family of novel recoupling pulse sequences, called three pulse recoupling. These pulse sequences can be employed for both homonuclear and heteronuclear recoupling experiments and are robust to dispersion in chemical shifts and rf-inhomogeneity. These recoupling pulse sequences can be used in design of two-dimensional solid state NMR experiments that use powdered dephased antiphase coherence (γ preparation) to encode chemical shifts in the indirect dimension. Both components of this chemical shift encoded gamma-prepared states can be refocused into inphase coherence by a recoupling element. This helps to achieve sensitivity enhancement in 2D NMR experiments by quadrature detection.

  20. Uranium mass transfer in a pulsed column

    Mass transfer measurements were made in a pulsed plate liquid-liquid extraction column. A depleted uranium solute was transferred between nitric acid and tributyl phosphate in odourless kerosene. Uranium concentration profiles of both phases were measured using a new design of sample collector. Heights of transfer units and mass transfer coefficients were calculated under a variety of pulsing conditions for both forward and back extraction. Under backwash conditions the value of HTU was found to decrease with increasing pulse velocity. Under extract conditions the HTU was found to be substantially constant over the range of pulse velocities investigated. (author)

  1. Pulse front control with adaptive optics

    Sun, B.; Salter, P. S.; Booth, M. J.

    2016-03-01

    The focusing of ultrashort laser pulses is extremely important for processes including microscopy, laser fabrication and fundamental science. Adaptive optic elements, such as liquid crystal spatial light modulators or membrane deformable mirrors, are routinely used for the correction of aberrations in these systems, leading to improved resolution and efficiency. Here, we demonstrate that adaptive elements used with ultrashort pulses should not be considered simply in terms of wavefront modification, but that changes to the incident pulse front can also occur. We experimentally show how adaptive elements may be used to engineer pulse fronts with spatial resolution.

  2. Ultrashort Laser Pulses in Biology and Medicine

    Braun, Markus; Zinth, Wolfgang

    2008-01-01

    Sources of ultrashort laser pulses are nowadays commercially available and have entered many areas of research and development. This book gives an overview of biological and medical applications of these laser pulses. The briefness of these laser pulses permits the tracing of the fastest processes in photo-active bio-systems, which is one focus of the book. The other focus is applications that rely on the high peak intensity of ultrashort laser pulses. Examples covered span non-linear imaging techniques, optical tomography, and laser surgery.

  3. Graphene in Ultrafast and Ultrastrong Laser Pulses

    Koochakikelardeh, Hamed; Apalkov, Vadym; Stockman, Mark

    2015-03-01

    We have shown that graphene subjected to an ultrafast (near-single-oscillation pulse) and strong (F ~ 1-3 V/Å) pulse exhibits fundamental behavior dramatically different from both insulators and metals. In such an ultrafast and ultrastrong field, the electron dynamics is coherent, in contrast to relatively long pulses (τ>100 fs) where the electron's dephasing becomes important leading to incoherent dynamics. Electron transfer from the valence band (VB) to the conduction band (CB) is deeply irreversible i.e., non-adiabatic, in which the residual CB population (after pulse ends) is close to the maximum one. The residual CB population as a function of wave vector is nonuniform with a few strongly localized spots near the Dirac points, at which the CB population is almost 100%. Furthermore, it is shown the direction of charge transfer depends on the pulse amplitude. Namely, at small pulse amplitude, =1 V/Å, it is in opposite direction of the pulse maximum (negative transferred charge). Consequently, in terms of charge transport, graphene at small pulse intensities behaves as a dielectric while at large intensities acts as a metal. These femtosecond currents and charge transfer in graphene may provide fundamental basis for detection and calibration of ultrashort intense laser pulses and are promising for petahertz information processing. This work was supported by U.S. Office of Naval Research No. N00014-13-1-0649 and NSF Grant No. ECCS-1308473.

  4. Conscious Pulse II: The rules of engagement

    Mould, Richard A

    2002-01-01

    This is the final paper in a series that considers the rules of engagement between conscious states and physiological states. In this paper, we imagine that an endogenous quantum mechanical superposition is created by a classical stimulus, and that this leads to a `physiological pulse' of states that are in superposition with one another. This pulse is correlated with a `conscious pulse' of the kind discussed in a previous paper (Conscious Pulse I). We then add a rule (5) to the four rules pr...

  5. Pulsed Single Frequency MOPA Laser Project

    National Aeronautics and Space Administration — Latest advances in semiconductor optoelectronics makes it possible to develop compact light weight robust sources of coherent optical pulses, demanded for numerous...

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

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

    2016-09-01

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

  7. Pulsed electrodeposition of Cu2ZnSnS4 thin films: Effect of pulse potentials

    Gurav, K. V.; Kim, Y. K.; Shin, S. W.; Suryawanshi, M. P.; Tarwal, N. L.; Ghorpade, U. V.; Pawar, S. M.; Vanalakar, S. A.; Kim, I. Y.; Yun, J. H.; Patil, P. S.; Kim, J. H.

    2015-04-01

    Cu2ZnSnS4 (CZTS) thin films are electrodeposited on Mo substrate using pulsed electrodeposition (PED) at different pulse potentials. The pulse potential (V1) is varied from 0 V/SCE to -0.9 V/SCE and V2 fixed at -1.1 V/SCE. The effects of pulse potentials on the properties of CZTS thin films are investigated. Formation of secondary phases along with CZTS phase is evident for films deposited at low pulse potentials. The secondary phases seem to be reduced with increase in pulse potentials. The morphology of CZTS films is systematically evolved from agglomerated grains to compact one with increase in pulse potentials. The film deposited using optimized pulse potentials (V1 - -0.9 V/SCE and V2 - -1.1 V/SCE) exhibit prominent CZTS phase with nearly stoichiometric composition and has compact morphology with optical band gap energy of 1.46 eV.

  8. Double-pulse LIBS of gadolinium oxide ablated by femto- and nano-second laser pulses

    Emission characteristics of gadolinium (Gd) oxide are studied, using ns and fs laser pulses for ablation in double-pulse laser induced breakdown spectroscopy (LIBS). In the current conditions of pulse energy and signal detection timing, emission intensity enhancement in the reheating mode is 25-fold, but little effect can be observed in a pre-pulse mode. It is shown that the optimum focus position of the ablation pulse is about 5 mm apart from the sample surface in the reheating mode. Although little emission can be observed in the single-pulse configuration with fs ablation pulses, the intense emission can be observed in the reheating mode in the double-pulse configuration. (orig.)

  9. Swift Observations of Gamma-Ray Burst Pulse Shapes: GRB Pulse Spectral Evolution Clarified

    Hakkila, Jon; Lien, Amy; Sakamoto, Takanori; Morris, David; Neff, James E.; Giblin, Timothy W.

    2015-12-01

    Isolated Swift gamma-ray burst (GRB) pulses, like their higher-energy BATSE counterparts, emit the bulk of their pulsed emission as a hard-to-soft component that can be fitted by the Norris et al. empirical pulse model. This signal is overlaid by a fainter, three-peaked signal that can be modeled by the residual fit of Hakkila & Preece: the two fits combine to reproduce GRB pulses with distinctive three-peaked shapes. The precursor peak appears on or before the pulse rise and is often the hardest component, the central peak is the brightest, and the decay peak converts exponentially decaying emission into a long, soft, power-law tail. Accounting for systematic instrumental differences, the general characteristics of the fitted pulses are remarkably similar. Isolated GRB pulses are dominated by hard-to-soft evolution; this is more pronounced for asymmetric pulses than for symmetric ones. Isolated GRB pulses can also exhibit intensity tracking behaviors that, when observed, are tied to the timing of the three peaks: pulses with the largest maximum hardnesses are hardest during the precursor, those with smaller maximum hardnesses are hardest during the central peak, and all pulses can re-harden during the central peak and/or during the decay peak. Since these behaviors are essentially seen in all isolated pulses, the distinction between “hard-to-soft and “intensity-tracking” pulses really no longer applies. Additionally, the triple-peaked nature of isolated GRB pulses seems to indicate that energy is injected on three separate occasions during the pulse duration: theoretical pulse models need to account for this.

  10. Efficient chirped-pulse amplification of sub-20 fs laser pulses

    Matsuoka, Shinichi; Yamakawa, Koichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    We have developed a model for ultrabroadband and ultrashort pulse amplification including the effects of a pulse shaper for regenerative pulse shaping, gain narrowing and gain saturation in the amplifiers. Thin solid etalons are used to control both gain narrowing and gain saturation during amplification. This model has been used to design an optimized Ti:sapphire amplifier system for producing efficiently pulses of < 20-fs duration with approaching peak and average powers of 100 TW and 20 W. (author)

  11. Fiber Optical Parametric Chirped Pulse Amplification of Sub-Picosecond Pulses

    Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Da Ros, Francesco;

    2013-01-01

    We demonstrate experimentally, for the first time to our knowledge, fiber optical parametric chirped pulse amplification of 400-fs pulses. The 400-fs signal is stretched, amplified by 26 dB and compressed back to 500 fs.......We demonstrate experimentally, for the first time to our knowledge, fiber optical parametric chirped pulse amplification of 400-fs pulses. The 400-fs signal is stretched, amplified by 26 dB and compressed back to 500 fs....

  12. Pulse retiming based on XPM using parabolic pulses formed in a fiber Bragg grating

    Parmigiani, F.; Petropoulos, P.; Ibsen, M.; Richardson, D.J.

    2006-01-01

    We experimentally demonstrate a novel all-optical all-fiberized pulse retiming scheme incorporating parabolic pulses generated in a linear fashion through pulse shaping in a superstructured fiber Bragg grating. The scheme relies on chirping the signal to be retimed using cross-phase modulation with the broader parabolic clock pulses, and subsequently retiming it through linear propagation in a dispersive medium. We demonstrate the cancellation of up to 4-ps root-mean-square timing jitter for ...

  13. Optimization of Pulse Temporal Contrast in Optical Parametric Chirped Pulse Amplification

    WANG Yan-Hai; PAN Xue; LI Xue-Chun; LIN Zun-Qi

    2009-01-01

    In optical parametric chirped pulse amplification (OPCPA), the degradation of temporal contrast of the com-pressed signal pulse mainly results from spectral clipping in the grating stretcher with finite size of the optics, parametric fluorescence (PF) and the spectral variations transferred from temporal fluctuation of the pump pulse. The temporal contrast of the recompressed amplified pulse in the OPCPA system is studied numerically and a number of solutions are considered and optimized to achieve the highest temporal contrast.

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

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

    2006-01-01

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

  15. Few-cycle isolated attosecond pulses

    Complete test of publication follows. In the last few years the field of attosecond science has shown impressive and rapid progress, mainly due to the introduction of novel experimental methods for the characterization of extreme ultraviolet (XUV) pulses and attosecond electron wave packets. This development has been also triggered by significant improvements in the control of the electric field of the driving infrared pulses. Particularly interesting for the applications is the generation of isolated attosecond XUV pulses using few-cycle driving pulses. In this case significant progresses have been achieved thanks to the stabilization of the carrier-envelope phase (CEP) of amplified light pulses. In this work we demonstrate that the polarization gating (PG) method with few-cycle phase-stabilized driving pulses allows one to generate few-cycle isolated attosecond pulses tunable on a very broad spectral region. The PG method is based on temporal modulation of the ellipticity of a light pulse, which confines the XUV emission in the temporal gate where the polarization is close to linear. The time-dependent polarization of phase-stabilized sub-6-fs pulses, generated by the hollow fiber technique, has been obtained using two birefringent plates. It is possible to create a linear polarization gate, whose position is imposed by the intensity profile of the pulse whilst the emission time is linked to the CEP of the electric field. The pulses have been analyzed by using a flat-field spectrometer. Continuous XUV spectra, corresponding to the production of isolated attosecond pulses, have been generated for particular CEP values. Upon changing the rotation of the first plate it was possible to tune the XUV emission in a broad spectra range. We have then achieved a complete temporal characterization of the generated isolated attosecond pulses using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG CRAB). The measured parabolic phase

  16. Increasing voltage of high power electric pulses by means of a pulse transformer

    Vdovin, S.S.

    1985-07-01

    The production of megavolt and terawatt electric pulses is difficult and complex. A component part of this problem is increasing the voltage of power pulses of the primary generators used. The problem of increasing the voltage of these pulses can be solved by the use of pulse transformers. However, due to the great voltages and power involved, it is necessary to establish the possibility in principle of increasing voltages to several megavolts, as well as the suitability of the technical and economic characteristics of pulse transformers designed for these purposes. Calculations performed in this article indicate that with pulse lengths of over 1 microsecond, pulse transformers can yield sufficiently high voltages with very slight distortions of transformed pulse shape and power losses. The use of pulse transformers is therefore effective and expedient at pulse lengths of over 1 microsecond. At lengths of less than 0.02 microsecond, pulse transformers apparently became undesirable due to low pulse voltages, great peak distortions and low efficiency.

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

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

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

  18. Effect of Pulsed Blowing on Farfield Noise

    Gaeta, R. J.; Ahuja, K. K.; Hellman, B.; Combier, R.

    2003-01-01

    This portion of the report documents the results of an experimental program, which focused on pulsed blowing from the trailing edge of a CCW. The main objective of this study was to assess whether pulsed blowing resulted in more, less, or the same amount of radiated noise to the farfield. Results show that a reduction in far-field noise of up to 5 dB is measured when pulse flow is compared to steady flow for an equivalent lift configuration. This reduction is in the spectral region associated with the trailing edge jet noise. This result is due to the unique advantage that pulsed flow has over steady flow. For a range of frequencies, more lift is experienced with the same mass flow as the steady case. Thus, for an equivalent lift and slot height, the pulsed system can operate at lower jet velocities, and hence lower jet noise. At low frequencies (below 1 kHz), the pulsed flow configuration generated more noise in the farfield. This is most likely due to the pulsing mechanism itself. Since the high pressure air feeding the pulsing mechanism was first passed through a high performance muffler, it is likely that this increase in not due to upstream valve noise. Most likely, the impulsive component of the air that periodically fills the plenum causes a broadband source that reaches the farfield. Although the benefit of a pulse trailing edge jet is evident from a mass flow usage and jet noise perspective, attention should be paid towards the design of a viable pulsing system. Future research program in this area should concentrate on the development of a "quiet" pulsing device.

  19. Pre-pulse irradiation examination, NSRR pulse irradiation and post-pulse irradiation examination of MH-1 fuel rod

    The Nuclear Safety Research Reactor (NSRR) program for studying failure threshold of pre-irradiated LWR fuel under simulated reactivity initiated accident conditions is in progress. In this program a 14 x 14 PWR type fuel K4-1 was segmented from K4/G08 long size PWR rod pre-irradiated in MIHAMA Unit-2 and was pulse irradiated on November 28, 1989 at NSRR. Energy deposition given to the test rod was 60 cal/g·fuel. No failure indication was observed by in-core monitoring and by post-pulse irradiation examination. As one of the NSRR data base on fuel behavior during transient/RIA, data obtained from pre-pulse irradiation examination, during NSRR pulse irradiation, and from post-pulse irradiation examination are summarized. (author)

  20. Pre-pulse irradiation examination, NSRR pulse irradiation and post-pulse irradiation examination of MH-2 fuel rod

    The Nuclear Safety Research Reactor (NSRR) program for studying failure threshold of pre-irradiated LWR fuel under simulated reactivity initiated accident conditions is in progress. In this program, a 14 x 14 PWR type fuel K4-2 was segmented from a K4/G08 long size PWR rod pre-irradiated in MIHAMA Unit-2 and was pulse irradiated on March 8, 1990 at NSRR. Energy deposition given to the test rod was 68 cal/g·fuel. No failure indication was observed by in-core monitoring and by post-pulse irradiation examination. As one of the NSRR data base on fuel behavior during transient/RIA, data obtained from pre-pulse irradiation examination, during NSRR pulse irradiation, and from post-pulse irradiation examination are summarized. (author)

  1. Academic Training - Pulsed SC Magnets

    Françoise Benz

    2006-01-01

    2005-2006 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 2, 3, June 29, 30, 31 May, 1, 2 June 11:00-12:00 - Auditorium, bldg 500 Pulsed SC Magnets by M. Wilson Lecture 1. Introduction to Superconducting Materials Type 1,2 and high temperature superconductors; their critical temperature, field & current density. Persistent screening currents and the critical state model. Lecture 2. Magnetization and AC Loss How screening currents cause irreversible magnetization and hysteresis loops. Field errors caused by screening currents. Flux jumping. The general formulation of ac loss in terms of magnetization. AC losses caused by screening currents. Lecture 3. Twisted Wires and Cables Filamentary composite wires and the losses caused by coupling currents between filaments, the need for twisting. Why we need cables and how the coupling currents in cables contribute more ac loss. Field errors caused by coupling currents. Lecture 4. AC Losses in Magnets, Cooling and Measurement Summary of all loss mech...

  2. X spectrometry with pulse detectors

    A comparison is made of various types of pulse X-ray detectors (scintillators + photomultipliers, proportional counters, ionisation chambers, semi-conductor detectors: Si (Li) and Ge (Li) ) as well as of their associated electronic equipment, from the point of view of the resolving power, the detection efficiency and the working surface, for photons of from 100 eV to 100 KeV. Semiconductor detectors (Si (Li) up to 50 KeV, Ge (Li) from 10 KeV up to 100 KeV) should rapidly find uses in all cases where an excellent resolving power is necessary (in X-fluorescence for example), whereas proportional counters present greater advantages for applications calling for a high detection surface, and also for very soft X-rays because the window of the detector can be very thin. (author)

  3. Terahertz pulsed imaging in vivo

    Pickwell-MacPherson, E.

    2011-03-01

    Terahertz (1012 Hz) pulsed imaging is a totally non-destructive and non-ionising imaging modality and thus potential applications in medicine are being investigated. In this paper we present results using our hand-held terahertz probe that has been designed for in vivo use. In particular, we use the terahertz probe to perform reflection geometry in vivo measurements of human skin. The hand-held terahertz probe gives more flexibility than a typical flat-bed imaging system, but it also results in noisier data and requires existing processing methods to be improved. We describe the requirements and limitations of system geometry, data acquisition rate, image resolution and penetration depth and explain how various factors are dependent on each other. We show how some of the physical limitations can be overcome using novel data processing methods.

  4. Background radiation from fission pulses

    England, T.R.; Arthur, E.D.; Brady, M.C.; LaBauve, R.J.

    1988-05-01

    Extensive source terms for beta, gamma, and neutrons following fission pulses are presented in various tabular and graphical forms. Neutron results from a wide range of fissioning nuclides (42) are examined and detailed information is provided for four fuels: /sup 235/U, /sup 238/U, /sup 232/Th, and /sup 239/Pu; these bracket the range of the delayed spectra. Results at several cooling (decay) times are presented. For ..beta../sup -/ and ..gamma.. spectra, only /sup 235/U and /sup 239/Pu results are given; fission-product data are currently inadequate for other fuels. The data base consists of all known measured data for individual fission products extensively supplemented with nuclear model results. The process is evolutionary, and therefore, the current base is summarized in sufficient detail for users to judge its quality. Comparisons with recent delayed neutron experiments and total ..beta../sup -/ and ..gamma.. decay energies are included. 27 refs., 47 figs., 9 tabs.

  5. Magnetic pulse cleaning of products

    Smolentsev, V. P.; Safonov, S. V.; Smolentsev, E. V.; Fedonin, O. N.

    2016-04-01

    The article deals with the application of a magnetic impact for inventing new equipment and methods of cleaning cast precision blanks from fragile or granular thickened surface coatings, which are difficult to remove and highly resistant to further mechanical processing. The issues relating to a rational use of the new method for typical products and auxiliary operations have been studied. The calculation and design methods have been elaborated for load-carrying elements of the equipment created. It has been shown, that the application of the magnetic pulse method, combined with a low-frequency vibration process is perspective at enterprises of general and special machine construction, for cleaning lightweight blanks and containers, used for transporting bulk goods.

  6. Pulsed laser irradiation of silicon

    Pulsed laser irradiation of silicon was investigated with a ruby laser. Development of heat flow theory made it possible to calculate temperature profiles in silicon during pulsed laser irradiation. Silicon self-diffusion measurements, laser annealing of damage in As implanted silicon, and laser induced doping of single crystal silicon was investigated. A computer programme was writen based on the numerical solution, and was used to calculate the temperature profiles in silicon during irradiation. Radioactive 31Si was used to determine the self-diffusion of silicon in silicon during irradiation. Radioactivity profiles in the silicon sample were measured by anodic oxidation, sequential removal of the formed SiO2 by etching in dilute HF and measurement of the radioactivity left in the sample. Spreading of the radioactive silicon marker started to take place at energy densities above 0.8 Jcm-2, giving an average duffusion coefficient of (5.0 ± 2.7) x 10-8 m2s-1, which is of the order of magnitude expected when melting takes place. The doping of silicon with Sb, Bi and In by laser assisted diffusion was investegated from evaporated layers as well as solutions of these dopants. The threshold energies for doping was 0.6, 0.9 and 0.7 Jcm-2, while maximum dopant concentrations of 2 x 1021, 7 x 1020 and 4 x 1020 respectively was found for Sb, Bi and In. These values exceed the equilibrium solid solubility by orders of magnitude, and can be ascribed to trapping of the dopant atoms, due to the high recrystallization velocities involved. Doping was carried out by placing silicon substrates directly into solutions of SbCl3 and triphenyl antimony. The threshold of solution doping was found to be much greater than doping from evaporated layer. This difference could be ascribed to the much larger absorption coefficient of the laser light in the evaporated layers, as compared to single crystal silicon

  7. Supercapacitors and electrochemical pulse sources

    Huggins, R.A. [Christian-Albrechts-Universitaet zu Kiel, Kaiserstrasse 2, D-24143 Kiel (Germany)

    2000-10-01

    Although often thought of as an area of low technology that is stagnant and uninteresting in the past, the use of electrochemical cells for energy storage and conversion purposes has received greatly increased attention recently. There are two general directions of interest. One is the long term goal of the development of electrical propulsion for vehicles, and the other is the rapid growth of portable electronic devices that require power sources with maximum energy content and the lowest possible size and weight. Most of the activities have been aimed at the development of electrochemical cells that are optimized toward either maximum specific energy or energy density. On the other hand, some of the current applications require electrical energy at high power levels for short times. These include very short pulses for digital electronic devices, the somewhat longer power pulse demands of some implantable medical devices, and the much larger transient power needs in connection with vehicle traction. Several mechanisms can be used to provide short term energy, and they have fundamentally different characteristics, and thus are potentially applicable to different types of transient output requirements. Some of these provide behavior that is analogous to an electrical capacitor, whereas others have more the character of batteries. The several electrochemical methods that can be used to evaluate the critical materials parameters in materials that might be applicable to such applications are discussed, as well as the use of LaPlace transform methods to convert information about the physical mechanisms and parameters of individual components into the dynamic response of an electrochemical system.

  8. Aerospace applications of pulsed plasmas

    Starikovskiy, Andrey

    2012-10-01

    The use of a thermal equilibrium plasma for combustion control dates back more than a hundred years to the advent of internal combustion (IC) engines and spark ignition systems. The same principles are still applied today to achieve high efficiency in various applications. Recently, the potential use of nonequilibrium plasma for ignition and combustion control has garnered increasing interest due to the possibility of plasma-assisted approaches for ignition and flame stabilization. During the past decade, significant progress has been made toward understanding the mechanisms of plasma chemistry interactions, energy redistribution and the nonequilibrium initiation of combustion. In addition, a wide variety of fuels have been examined using various types of discharge plasmas. Plasma application has been shown to provide additional combustion control, which is necessary for ultra-lean flames, high-speed flows, cold low-pressure conditions of high-altitude gas turbine engine (GTE) relight, detonation initiation in pulsed detonation engines (PDE) and distributed ignition control in homogeneous charge-compression ignition (HCCI) engines, among others. The present paper describes the current understanding of the nonequilibrium excitation of combustible mixtures by electrical discharges and plasma-assisted ignition and combustion. Nonequilibrium plasma demonstrates an ability to control ultra-lean, ultra-fast, low-temperature flames and appears to be an extremely promising technology for a wide range of applications, including aviation GTEs, piston engines, ramjets, scramjets and detonation initiation for pulsed detonation engines. To use nonequilibrium plasma for ignition and combustion in real energetic systems, one must understand the mechanisms of plasma-assisted ignition and combustion and be able to numerically simulate the discharge and combustion processes under various conditions.

  9. Laser system using ultra-short laser pulses

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

    2009-10-27

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

  10. A self-reset circuit of pulse transformer

    A self-reset circuit of pulse transformer is introduced. Using this method, the distortion of output pulse waveform is decreased, pulse transformer can operate normally when pulse high voltage is raised from zero to design value, and it is unnecessary to use additional reset power supply or to increase the turns of pulse transformer primary winding and the volume of core

  11. Design of a Compact Pulsed Power Accelerator

    2011-01-01

    A 100 kA/60 ns compact pulsed power accelerator was designed to study the influence to the X-pinch by the load. It is composed of a Marx generator, a combined pulse forming (PFL), a gas-filled V/N field distortion switch, a transfer line,

  12. Pulsed electric field inactivation in a microreactor

    Fox, M.B.

    2006-01-01

    Pulsed electric fields (PEF) is a novel, non-thermal pasteurization method which uses short, high electric field pulses to inactivate microorganisms. The advantage of a pasteurization method like PEF compared to regular heat pasteurization is that the taste, flavour, texture and nutritional value ar

  13. High reliability low jitter pulse generator

    Savage, Mark E.; Stoltzfus, Brian S.

    2013-01-01

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

  14. Nasal pulse oximetry overestimates oxygen saturation

    Rosenberg, J; Pedersen, M H

    1990-01-01

    Ten surgical patients were monitored with nasal and finger pulse oximetry (Nellcor N-200) for five study periods with alternating mouth and nasal breathing and switching of cables and sensors. Nasal pulse oximetry was found to overestimate arterial oxygen saturation by 4.7 (SD 1.4%) (bias and...

  15. Nanosecond pulse generators for induction linear accelerators

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

  16. Electric pulse generator with a saturable inductance

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

  17. Colliding pulse mode-locked VECSEL

    Marah, Declan; Laurain, Alexandre; Stolz, Wolfgang; Koch, Stephan; Ruiz Perez, Antje; McInerney, John; Moloney, Jerome

    2016-03-01

    Recent development of high power femtosecond pulse modelocked VECSEL with gigahertz pulse repetition rates sparked an increased interest from the scientific community due to the broad field of applications for such sources, such as frequency metrology, high-speed optical communication systems or high-resolution optical sampling. To the best of our knowledge, we report for the first time a colliding pulse modelocked VECSEL, where the VECSEL gain medium and a semiconductor saturable absorber (SESAM) are placed inside a ring cavity. This cavity geometry provides both a practical and an efficient way to get optimum performance from a modelocked laser system. The two counter propagating pulses in our ring cavity synchronize in the SESAM because the minimum energy is lost when they saturate the absorber together. This stronger saturation of the absorber increases the stability of the modelocking and reduces the overall losses of the laser for a given intra-cavity fluence, leading to a lower modelocking threshold. This also allows the generation of fundamental modelocking at a relatively low repetition rate (power compared to conventional VECSEL cavity. We obtained a total output power of 2.2W with an excellent beam quality, a pulse repetition rate of 1GHz and a pulse duration ranging from 1ps to 3ps. The emitted spectrum was centered at 1007nm with a FWHM of 3.1nm, suggesting that shorter pulses can be obtained with adequate dispersion compensation. The laser characteristics such as the pulse duration and stability are studied in detail.

  18. Low power arcjet thruster pulse ignition

    Sarmiento, Charles J.; Gruber, Robert P.

    1987-01-01

    An investigation of the pulse ignition characteristics of a 1 kW class arcjet using an inductive energy storage pulse generator with a pulse width modulated power converter identified several thruster and pulse generator parameters that influence breakdown voltage including pulse generator rate of voltage rise. This work was conducted with an arcjet tested on hydrogen-nitrogen gas mixtures to simulate fully decomposed hydrazine. Over all ranges of thruster and pulser parameters investigated, the mean breakdown voltages varied from 1.4 to 2.7 kV. Ignition tests at elevated thruster temperatures under certain conditions revealed occasional breakdowns to thruster voltages higher than the power converter output voltage. These post breakdown discharges sometimes failed to transition to the lower voltage arc discharge mode and the thruster would not ignite. Under the same conditions, a transition to the arc mode would occur for a subsequent pulse and the thruster would ignite. An automated 11 600 cycle starting and transition to steady state test demonstrated ignition on the first pulse and required application of a second pulse only two times to initiate breakdown.

  19. Pulsed power liner for PLT energy systems

    PLT is Princeton University's latest Tokamak machine in the controlled thermonuclear fusion research effort. The OH (ohmic heating) and SF (shaping field) systems for the machine place a very high energy pulsed current load on the AC line feeding them. This paper describes the two systems and the steps taken to insure minimum effect on line regulation during the pulsed operation

  20. CLASSIFICATION OF PULSE ARC WELDING PROCESSES

    KRAMPIT A.G.; KRAMPIT N.Y.; KRAMPIT M.A.; DMITRIEVA A.V.

    2012-01-01

    Pulse welding processes improve productivity; also they allow welding of thin sheets of metal without penetration. Splashing and expenses for cleaning surfaces from droplets are also reduced. Pulse welding processes have a wholesome effect on seam formation at the expenses of thermal exposure on welding puddle and HAZ.

  1. Pulsed DC accelerator for laser wakefield accelerator

    For the acceleration of ultra-short, high-brightness electron bunches, a pulsed DC accelerator was constructed. The pulser produced megavolt pulses of 1 ns duration in a vacuum diode. Results are presented from field emission of electrons in the diode. The results indicate that the accelerating gradient in the diode is approximately 1.5 GV/m

  2. Bipolar high voltage pulse power generator

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

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

  3. Thermodynamic analysis of a pulse tube engine

    Highlights: ► Numerical model of the pulse tube engine process. ► Proof that the heat transfer in the pulse tube is out of phase with the gas velocity. ► Proof that a free piston operation is possible. ► Clarifying the thermodynamic working principle of the pulse tube engine. ► Studying the influence of design parameters on the engine performance. - Abstract: The pulse tube engine is an innovative simple heat engine based on the pulse tube process used in cryogenic cooling applications. The working principle involves the conversion of applied heat energy into mechanical power, thereby enabling it to be used for electrical power generation. Furthermore, this device offers an opportunity for its wide use in energy harvesting and waste heat recovery. A numerical model has been developed to study the thermodynamic cycle and thereby help to design an experimental engine. Using the object-oriented modeling language Modelica, the engine was divided into components on which the conservation equations for mass, momentum and energy were applied. These components were linked via exchanged mass and enthalpy. The resulting differential equations for the thermodynamic properties were integrated numerically. The model was validated using the measured performance of a pulse tube engine. The transient behavior of the pulse tube engine’s underlying thermodynamic properties could be evaluated and studied under different operating conditions. The model was used to explore the pulse tube engine process and investigate the influence of design parameters.

  4. Nova pulse power system description and status

    The Nova laser system is designed to produce critical data in the nation's inertial confinement fusion effort. It is the world's largest peak power laser and presents various unique pulse power problems. In this paper, pulse power systems for this laser are described, the evolutionary points from prior systems are pointed out, and the current status of the hardware is given

  5. Pulse interaction in nonlinear vacuum electrodynamics

    Ignatov, A. M.; Poponin, V. P.

    2000-01-01

    The energy-momentum conservation law is used to investigate the interaction of pulses in the framework of nonlinear electrodynamics with Lorentz-invariant constitutive relations. It is shown that for the pulses of the arbitrary shape the interaction results in phase shift only.

  6. Optimization of the LCLS Single Pulse Shutter

    Adera, Solomon; /Georgia Tech., Atlanta /SLAC

    2010-08-25

    A mechanical shutter which operates on demand is used to isolate a single pulse from a 120 Hz X-ray source. This is accomplished with a mechanical shutter which is triggered on demand with frequencies ranging from 0 to 10 Hz. The single pulse shutter is an iron blade that oscillates on a pivot in response to a force generated by a pair of pulsed electromagnets (current driven teeter-totter). To isolate an individual pulse from the X-ray beam, the motion of the mechanical shutter should be synchronized in such a way that it allows a single pulse to pass through the aperture and blocks the other incoming pulses. Two consecutive pulses are only {approx} 8 ms apart and the shutter is required to complete one full cycle such that no two pulses pass through the opening. Also the opening of the shutter blade needs to be at least 4 mm so that a 1 mm diameter rms Gaussian beam can pass through without modulation. However, the 4 mm opening is difficult to obtain due to blade rebound and oscillation of the blade after colliding with the electromagnet. The purpose of this project is to minimize and/or totally eliminate the rebound of the shutter blade in pursuit of maximizing the aperture while keeping the open window interval < {approx}12 ms.

  7. Methods for High Power EM Pulse Measurement

    P. Fiala

    2006-12-01

    Full Text Available There are some suitable methods for the measurement of ultra-short solitary electromagnetic pulses that can be generated by high power pulsed generators. The measurement methods properties have to correspond to the fact whether we want to measure pulses of voltage, current or free-space electromagnetic wave. The need for specific measurement methods occurred by the development of high power microwave pulse generator. Applicable methods are presented in this paper. The method utilizing Faraday's induction law allows the measurement of generated current. For the same purpose the magneto-optic method can be utilized, with its advantages. For measurement of output microwave pulse of the generator the calorimetric method was designed and realized.

  8. Analysis of Picosecond Pulsed Laser Melted Graphite

    Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M. S.; Huang, C. Y.; Malvezzi, A. M.; Bloembergen, N.

    1986-12-01

    A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm{sup -1} and the disorder-induced mode at 1360 cm{sup -1}, the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nanosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence.

  9. One laser pulse generates two photoacoustic signals

    Gao, Fei; Zheng, Yuanjin

    2016-01-01

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

  10. Evolution of Striation in Pulsed Glow Discharges

    Liu, Yuanye; He, Feng; Zhao, Xiaofei; Ouyang, Jiting

    2016-01-01

    In this work, striations in pulsed glow discharges are studied by experiments and Particle-In-Cell/Monte Carlo Collision (PIC/MCC) simulation. The spatio-temporal evolution of the potential and the electron energy during the discharge are analyzed. The processes of striation formation in pulsed glow discharges and dielectric barrier discharges (DBD) are compared. The results show that the mechanisms of striation in pulsed DC discharge and DBD are similar to each other. The evolution of electron energy distribution function before and after the striation formation indicates that the striation results from the potential well of the space charge. During a pulsed breakdown, the striations are formed one by one towards the anode in a weak field channel. This indicates that the formation of striations in a pulsed discharge depends on the flow of modulated electrons. supported by National Natural Science Foundation of China (Nos. 10875010 and 11175017)

  11. A modularized pulse programmer for NMR spectroscopy

    A modularized pulse programmer for a NMR spectrometer is described. It consists of a networked PCI-104 single-board computer and a field programmable gate array (FPGA). The PCI-104 is dedicated to translate the pulse sequence elements from the host computer into 48-bit binary words and download these words to the FPGA, while the FPGA functions as a sequencer to execute these binary words. High-resolution NMR spectra obtained on a home-built spectrometer with four pulse programmers working concurrently demonstrate the effectiveness of the pulse programmer. Advantages of the module include (1) once designed it can be duplicated and used to construct a scalable NMR/MRI system with multiple transmitter and receiver channels, (2) it is a totally programmable system in which all specific applications are determined by software, and (3) it provides enough reserve for possible new pulse sequences

  12. Argonne National Laboratory superconducting pulsed coil program

    The main objectives are to develop high current (approx. 100 kA) cryostable cable configurations with reasonably low ac losses, to build a demonstration pulsed coil, and to develop a rather inexpensive large fiberglass reinforced helium cryostat. A 1.5-MJ cryostable pulsed superconducting coil has been developed and constructed at ANL. The coil has a peak field of 4.5 T at an operating current of 11.0 kA. A large inexpensive plastic cryostat has been developed for testing the pulsed coil. The coil has been pulsed with a maximum dB/dt of 11 T/s. The coil was pulsed more than 4000 cycles. Detailed results of the ac loss measurements and the current sharing of the cryostability will be described

  13. AN UPDATE ON NIF PULSED POWER

    Arnold, P A; James, G F; Petersen, D E; Pendleton, D L; McHale, G B; Barbosa, F; Runtal, A S; Stratton, P L

    2009-06-22

    The National Ignition Facility (NIF) is a 192-beam laser fusion driver operating at Lawrence Livermore National Laboratory. NIF relies on three large-scale pulsed power systems to achieve its goals: the Power Conditioning Unit (PCU), which provides flashlamp excitation for the laser's injection system; the Power Conditioning System (PCS), which provides the multi-megajoule pulsed excitation required to drive flashlamps in the laser's optical amplifiers; and the Plasma Electrode Pockels Cell (PEPC), which enables NIF to take advantage of a fourpass main amplifier. Years of production, installation, and commissioning of the three NIF pulsed power systems are now complete. Seven-day-per-week operation of the laser has commenced, with the three pulsed power systems providing routine support of laser operations. We present the details of the status and operational experience associated with the three systems along with a projection of the future for NIF pulsed power.

  14. Molecular wakes for ultrashort laser pulses

    2010-01-01

    The molecular wake-assisted interaction between two collinear femotosecond laser pulses is investigated in air,which leads to the generation of a controllable 1.8 mJ super-continuum pulse with an elongated self-guided channel due to the cross-phase modulation of the impulsively aligned diatomic molecules in air. For two parallel launched femtosecond laser pulses with a certain spatial separation,controllable attraction and repulsion of the pulses are observed due to the counter-balance among molecular wakes,Kerr and plasma effects,where the molecular wakes show a longer interaction distance than the others to control the propagation of the intense ultrashort laser pulses.

  15. Relativistic laser pulse compression in magnetized plasmas

    The self-compression of a weak relativistic Gaussian laser pulse propagating in a magnetized plasma is investigated. The nonlinear Schrödinger equation, which describes the laser pulse amplitude evolution, is deduced and solved numerically. The pulse compression is observed in the cases of both left- and right-hand circular polarized lasers. It is found that the compressed velocity is increased for the left-hand circular polarized laser fields, while decreased for the right-hand ones, which is reinforced as the enhancement of the external magnetic field. We find a 100 fs left-hand circular polarized laser pulse is compressed in a magnetized (1757 T) plasma medium by more than ten times. The results in this paper indicate the possibility of generating particularly intense and short pulses

  16. Filters for High Rate Pulse Processing

    Alpert, B K; Bennett, D A; Doriese, W B; Fowler, J W; Hoover, A S; Rabin, M W; Ullom, J N

    2012-01-01

    We introduce a filter-construction method for pulse processing that differs in two respects from that in standard optimal filtering, in which the average pulse shape and noise-power spectral density are combined to create a convolution filter for estimating pulse heights. First, the proposed filters are computed in the time domain, to avoid periodicity artifacts of the discrete Fourier transform, and second, orthogonality constraints are imposed on the filters, to reduce the filtering procedure's sensitivity to unknown baseline height and pulse tails. We analyze the proposed filters, predicting energy resolution under several scenarios, and apply the filters to high-rate pulse data from gamma-rays measured by a transition-edge-sensor microcalorimeter.

  17. MOPA pulsed fiber laser for silicon scribing

    Yang, Limei; Huang, Wei; Deng, Mengmeng; Li, Feng

    2016-06-01

    A 1064 nm master oscillator power amplifier (MOPA) pulsed fiber laser is developed with flexible control over the pulse width, repetition frequency and peak power, and it is used to investigate the dependence of mono-crystalline silicon scribe depth on the laser pulse width, scanning speed and repeat times. Experimental results indicate that long pulses with low peak powers lead to deep ablation depths. We also demonstrate that the ablation depth grows fast with the scanning repeat times at first and progressively tends to be saturated when the repeat times reach a certain level. A thermal model considering the laser pulse overlapping effect that predicts the silicon temperature variation and scribe depth is employed to verify the experimental conclusions with reasonably close agreement. These conclusions are of great benefits to the optimization of the laser material processing with high efficiency.

  18. Pulse oximetry in bronchiolitis: is it needed?

    Hendaus, Mohamed A; Jomha, Fatima A; Alhammadi, Ahmed H

    2015-01-01

    Infants admitted to health-care centers with acute bronchiolitis are frequently monitored with a pulse oximeter, a noninvasive method commonly used for measuring oxygen saturation. The decision to hospitalize children with bronchiolitis has been largely influenced by pulse oximetry, despite its questionable diagnostic value in delineating the severity of the illness. Many health-care providers lack the appropriate clinical fundamentals and limitations of pulse oximetry. This deficiency in knowledge might have been linked to changes in the management of bronchiolitis. The aim of this paper is to provide the current evidence on the role of pulse oximetry in bronchiolitis. We discuss the history, fundamentals of operation, and limitations of the apparatus. A search of the Google Scholar, Embase, Medline, and PubMed databases was carried out for published articles covering the use of pulse oximetry in bronchiolitis. PMID:26491341

  19. Generation of Femtosecond Electron and Photon Pulses

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

    2005-01-01

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

  20. Conscious Pulse II The rules of engagement

    Mould, R A

    2002-01-01

    This is the final paper in a series that considers the rules of engagement between conscious states and physiological states. In this paper, we imagine that an endogenous quantum mechanical superposition is created by a classical stimulus, and that this leads to a `physiological pulse' of states that are in superposition with one another. This pulse is correlated with a `conscious pulse' of the kind discussed in a previous paper (Conscious Pulse I). We then add a rule (5) to the four rules previously given. This rule addresses the effect of `pain' consciousness on both of these pulses, and in doing so, it validates the "Parallel Principle" applied to pain. Key words: Brain states, cat paradox, consciousness, conscious observer, macroscopic superposition, measurement, state reduction, state collapse, von Neumann.

  1. Short-pulse chemical beam epitaxy

    Zhang, Suian; Cui, Jie; Aoyagi, Yoshinobu (RIKEN, The Institute of Physical and Chemical Research, Saitama (Japan)); Tanaka, Akihiko (Bentec Co., Tokyo (Japan))

    1994-03-10

    Short-pulse chemical beam epitaxy has been proposed and studied. The short pulses with supersonic characteristics and a width of milliseconds were generated by high speed valves and the related pumping lines on a purpose-built CBE system. Using a time-of-fight technique, we verified the dependence of pulse properties on the source pressures and the valve on-time. The results indicate that modulation of molecular kinetic energy and accurate control of molecule supply were obtained. GaAs epitaxial growth with use of trimethylgallium pulses was carried out and investigated by means of RHEED (reflection high-energy electron diffraction) observation. It was demonstrated that the newly developed short-pulse chemical beam epitaxy has the advantage of high controllability

  2. Production of picosecond, kilojoule, and petawatt laser pulses via Raman amplification of nanosecond pulses.

    Trines, R M G M; Fiúza, F; Bingham, R; Fonseca, R A; Silva, L O; Cairns, R A; Norreys, P A

    2011-09-01

    Raman amplification in plasma has been promoted as a means of compressing picosecond optical laser pulses to femtosecond duration to explore the intensity frontier. Here we show for the first time that it can be used, with equal success, to compress laser pulses from nanosecond to picosecond duration. Simulations show up to 60% energy transfer from pump pulse to probe pulse, implying that multikilojoule ultraviolet petawatt laser pulses can be produced using this scheme. This has important consequences for the demonstration of fast-ignition inertial confinement fusion. PMID:21981507

  3. Pulse chirp increasing pulse compression followed by positive resonant radiation in fibers

    McLenaghan, Joanna

    2016-01-01

    Pulse self-compression followed by the generation of resonant radiation is a well known phenomenon in non-linear optics. Resonant radiation is important as it allows for efficient and tunable wavelength conversion. We vary the chirp of the initial pulse and find in simulations and experiments that a small positive chirp enhances the pulse compression and strongly increases the generation of resonant radiation. This result corroborates previously published simulation results indicating an improved degree of pulse compression for a small positive chirp [1]. It also demonstrates how pulse evolution can be studied without cutting back the fiber.

  4. Creation and control of single attosecond XUV pulse by few-cycle intense laser pulse

    Carrera, Juan J.; Tong, X. M.; Chu, Shih-I.

    2006-05-01

    We present a theoretical investigation of the mechanisms responsible for the production of single atto-second pulse by using few-cycle intense laser pulses. The atto-second XUV spectral is calculated by accurately integrating the time- dependent Schr"odinger equation. The detailed mechanism for the production of the XUV pulse are also corroborated by analyzing the classical trajectories of the electron. Our study shows that the first return of the rescattering electron is responsible for the high energy atto-second pulse. Furthermore, we can optimize the production of atto-second XUV pulses by modifying the trajectory of the rescattering electron by tuning the laser field envelope.

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

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

    2015-03-01

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

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

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

    2015-03-15

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

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

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

  8. Krytron switch for single pulse selection from a mode-locked pulse train

    We present detailed technical data on a Krytron switch circuit which is used for the single pulse selection from a pulse train of a mode-locked laser. Design considerations for the triggering circuit of the Krytron are described and the optimum selections of avalanche transistors are shown. Data on the delay time and life characteristics of Krytron tubes are shown. A very reliable pulse selection from a mode-locked pulse train has been realized. The amplitude variation of the selected pulse was less than +-2.5%. (author)

  9. A Compact Nanosecond-Pulse Shaping System Based on Pulse Stacking in Fibres

    SUI Zhan; LIN Hong-Huan; WANG Jian-Jun; ZHAO Hong-Ming; LI Ming-Zhong; QIAN Lie-Jia; ZHU He-Yuan; FAN Dian-Yuan

    2006-01-01

    @@ We demonstrate a compact pulse shaping system based on temporal stacking of pulses in fibres, by which synchronized pulses of ultrashort and nanosecond lasers can be obtained. The system may generate shape-controllable pulses with a fast rise time and high-resolution within a time window of ~2.2 ns by adjusting variable optical attenuators in the 32 fibre channels independently. With the help of optical amplifiers, the system delivers mJ-level pulses with a signal-to-noise ratio of~35 dB.

  10. SLAC pulsed x-ray facility

    The Stanford Linear Accelerator Center (SLAC) operates a high energy (up to 33 GeV) linear accelerator delivering pulses up to a few microseconds wide. The pulsed nature of the electron beam creates problems in the detection and measurement of radiation both from the accelerator beam and the klystrons that provide the rf power for the accelerator. Hence, a pulsed x-ray facility has been built at SLAC mainly for the purpose of testing the response of different radiation detection instruments to pulsed radiation fields. The x-ray tube consists of an electron gun with a control grid. This provides a stream of pulsed electrons that can be accelerated towards a confined target-window. The window is made up of aluminium 0.051 cm (20 mils) thick, plated on the vacuum side with a layer of gold 0.0006 cm (1/4 mil) thick. The frequency of electron pulses can be varied by an internal pulser from 60 to 360 pulses per second with pulse widths of 360 ns to 5 μs. The pulse amplitude can be varied over a wide range of currents. An external pulser can be used to obtain other frequencies or special pulse shapes. The voltage across the gun can be varied from 0 to 100 kV. The major part of the x-ray tube is enclosed in a large walk-in-cabinet made of 1.9 cm (3/4 in) plywood and lined with 0.32 cm (1/8 in) lead to make a very versatile facility. 3 refs., 5 figs

  11. Analytical model of the pulse tube engine

    The pulse tube engine represents the thermodynamic inversion of the pulse tube refrigerator used in cryogenic cooling applications. It has a high potential to be used as a prime mover for the conversion of low grade waste heat into mechanical or electrical energy. This paper describes an analytical analysis of the pulse tube engine based on a zero-dimensional model. During compression and expansion, the engine components are considered as isothermal with characteristic temperatures. At the piston's dead centers, a thermal relaxation model is used to switch between these temperatures. Analytical relations for the pV–work developed by the pulse tube engine and its efficiency are derived. The irreversible nature of the pulse tube engine is studied by calculating the entropy production in the components. Furthermore, the thermodynamic cycle is investigated analytically under variation of design features and operating conditions. The results are compared to prior numerical studies. The minimal temperature ratio above which the engine provides a work output is derived analytically and compared to experimental observations. Fundamental characteristics and application limitations of the pulse tube engine are disclosed. An upper limit for the efficiency of the pulse tube engine is derived theoretically and confirmed experimentally as well as through numerically calculations. - Highlights: • An analytical expression for the pV-work of the pulse tube engine is derived. • The irreversible nature of the pulse tube engine is shown mathematically. • The temperature ratio above which the engine operates is calculated and measured. • An upper limit for the pulse tube engine's efficiency is derived

  12. From quantum pulse gate to quantum pulse shaper-engineered frequency conversion in nonlinear optical waveguides

    Full control over the spatiotemporal structure of quantum states of light is an important goal in quantum optics, to generate, for instance, single-mode quantum pulses or to encode information on multiple modes, enhancing channel capacities. Quantum light pulses feature an inherent, rich spectral broadband-mode structure. In recent years, exploring the use of integrated optics as well as source engineering has led to a deep understanding of the pulse-mode structure of guided quantum states of light. In addition, several groups have started to investigate the manipulation of quantum states by means of single-photon frequency conversion. In this paper, we explore new routes towards complete control of the inherent pulse-modes of ultrafast pulsed quantum states by employing specifically designed nonlinear waveguides with adapted dispersion properties. Starting from our recently proposed quantum pulse gate (QPG), we further generalize the concept of spatiospectral engineering for arbitrary χ(2)-based quantum processes. We analyse the sum-frequency generation-based QPG and introduce the difference-frequency generation-based quantum pulse shaper (QPS). Together, these versatile and robust integrated optical devices allow for arbitrary manipulations of the pulse-mode structure of ultrafast pulsed quantum states. The QPG can be utilized to select an arbitrary pulse mode from a multimode input state, whereas the QPS enables the generation of specific pulse modes from an input wavepacket with a Gaussian-shaped spectrum.

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

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

  14. Single quantum path control by a fundamental chirped pulse combined with a subharmonic control pulse

    Feng, Liqiang [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Chu, Tianshu, E-mail: tschu008@163.com [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer HHG spectra and attosecond pulse generation from a model He atom. Black-Right-Pointing-Pointer Two-color laser field of a chirped fundamental pulse and a subharmonics control pulse. Black-Right-Pointing-Pointer Single quantum path selection by {beta} = 4.55 chirp pulse and the zero-phase 2000 nm control pulse. Black-Right-Pointing-Pointer Formation of 337 eV supercontinuum region and generation of 39 as pulse. -- Abstract: In this paper, we study the issue of single quantum path control and its role in attosecond pulse generation. By carrying out the time-dependent Schroedinger equation analysis for the harmonic emission from a single He atom irradiated by the two-color laser field, consisting of a short 800 fundamental chirped pulse and a subharmonic 800-2400 nm control pulse, we find that the most favorable condition for attosecond generation is at the fundamental chirp parameter {beta} = 4.55 together with the zero-phase 2000 nm control pulse, in which the single quantum path (short quantum path) is selected to contribute to the harmonic spectrum exhibiting an ultrabroad supercontinuum of a 337 eV bandwidth. Finally, an isolated attosecond pulse as short as 39 as is thus generated directly.

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

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

    2014-08-01

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

  16. Residual stress reduction by combined treatment of pulsed magnetic field and pulsed current

    Highlights: → The combination of magnetic field and current releases stress significantly. → Both magneto and electro-plasticity may exit in the combined treatment. → Stress increase caused by current should be studied later. - Abstract: This paper reports a significant decrease on residual stress by combined treatment of a pulsed magnetic field and a pulse current on steel samples with pre-induced residual stress conditions, compared to a separately single treatment by either the pulsed magnetic field or the pulsed current. Briefly, 10% stress decrease by pulsed magnetic field treatment and 20% increase by pulsed current treatment were observed respectively. While 60% stress release is achieved by the combined treatments, in which the same magnetic field and current parameters were applied. It is supposed that the magnetic field facilitates dislocations depinning and pulsed current provides conduction electrons to drive dislocations to move further and faster. The combined effects lead to electro-magneto-plasticity and further residual stress release.

  17. Intense isolated few-cycle attosecond XUV pulses from overdense plasmas driven by tailored laser pulses

    Chen, Zi-Yu; Li, Xiao-Ya; Chen, Li-Ming; Li, Yu-Tong; Zhu, Wen-Jun

    2014-06-01

    A method to generate an intense isolated few-cycle attosecond XUV pulse is demonstrated using particle-in-cell simulations. When a tailored laser pulse with a sharp edge irradiates a foil target, a strong transverse net current can be excited, which emits a few-cycle XUV pulse from the target rear side. The isolated pulse is ultrashort in the time domain with a duration of several hundred attoseconds. It also has a narrow bandwidth in the spectral domain compared to other XUV sources of high-order harmonics. It has most energy confined around the plasma frequency and no low-harmonic orders below the plasma frequency. It is also shown that XUV pulse of peak field strength up to $ 8\\times 10^{12} $ V$\\mathrm{m}^{-1}$ can be produced. Without the need for pulse selecting and spectral filtering, such an intense few-cycle XUV pulse is better suited to a number of applications.

  18. Intense isolated few-cycle attosecond XUV pulses from overdense plasmas driven by tailored laser pulses

    Chen, Zi-Yu; Chen, Li-Ming; Li, Yu-Tong; Zhu, Wen-Jun

    2014-01-01

    A method to generate an intense isolated few-cycle attosecond XUV pulse is demonstrated using particle-in-cell simulations. When a tailored laser pulse with a sharp edge irradiates a foil target, a strong transverse net current can be excited, which emits a few-cycle XUV pulse from the target rear side. The isolated pulse is ultrashort in the time domain with a duration of several hundred attoseconds. It also has a narrow bandwidth in the spectral domain compared to other XUV sources of high-order harmonics. It has most energy confined around the plasma frequency and no low-harmonic orders below the plasma frequency. In addition, the peak electric field of the pulse is up to $ 8\\times 10^{12} $ V$\\mathrm{m}^{-1}$. Without the need for pulse selecting and spectral filtering, such an intense few-cycle XUV pulse is better suited to a number of applications.

  19. Trends in ultrashort and ultrahigh power laser pulses based on optical parametric chirped pulse amplification

    Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992, optical parametric chirped pulse amplification (OPCPA) became the most promising method for the amplification of broadband optical pulses. In the meantime, we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers. The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level. Meanwhile, the output pulse duration based on optical parametric amplification has entered the range of few-optical-cycle field. In this paper, we overview the basic principles, trends in development, and current state of the ultrashort and laser systems based on OPCPA, respectively. (paper)

  20. ADRF experiments using near n.pi pulse strings. [Adiabatic Demagnetization due to Radio Frequency pulses

    Rhim, W. K.; Burum, D. P.; Elleman, D. D.

    1977-01-01

    Adiabatic demagnetization (ADRF) can be achieved in a dipolar coupled nuclear spin system in solids by applying a string of short RF pulses and gradually modulating the pulse amplitudes or pulse angles. This letter reports an adiabatic inverse polarization effect in solids and a rotary spin echo phenomenon observed in liquids when the pulse angle is gradually changed across integral multiples of pi during a string of RF pulses. The RF pulse sequence used is illustrated along with the NMR signal from a CaF2 single crystal as observed between the RF pulses and the rotary spin echo signal observed in liquid C6F6 for n = 2. The observed effects are explained qualitatively on the basis of average Hamiltonian theory.

  1. Charged particle interaction with a chirped electromagnetic pulse

    Khachatryan, A. G.; Boller, K. -J.; Goor, van, Fred

    2003-01-01

    It is found that a charged particle can get a net energy gain from the interaction with an electromagnetic chirped pulse. Theoretically, the energy gain increases with the pulse amplitude and with the relative frequency variation in the pulse.

  2. Intraband effects on ultrafast pulse propagation in semiconductor optical amplifier

    K Hussain; S K Varshney; P K Datta

    2010-11-01

    High bit-rate (>10 Gb/s) signals are composed of very short pulses and propagation of such pulses through a semiconductor optical amplifier (SOA) requires consideration of intraband phenomena. Due to the intraband effects, the propagating pulse sees a fast recovering nonlinear gain which introduces less distortion in the pulse shape and spectrum of the output pulse but introduces a positive chirping at the trailing edge of the pulse.

  3. Cascaded Soliton Compression of Energetic Femtosecond Pulses at 1030 nm

    Bache, Morten; Zhou, Binbin

    2012-01-01

    We discuss soliton compression with cascaded second-harmonic generation of energetic femtosecond pulses at 1030 nm. We discuss problems encountered with soliton compression of long pulses and show that sub-10 fs compressed pulses can be achieved.......We discuss soliton compression with cascaded second-harmonic generation of energetic femtosecond pulses at 1030 nm. We discuss problems encountered with soliton compression of long pulses and show that sub-10 fs compressed pulses can be achieved....

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

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

    2014-01-01

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

  5. Maximum likelihood estimation of the attenuated ultrasound pulse

    Rasmussen, Klaus Bolding

    1994-01-01

    The attenuated ultrasound pulse is divided into two parts: a stationary basic pulse and a nonstationary attenuation pulse. A standard ARMA model is used for the basic pulse, and a nonstandard ARMA model is derived for the attenuation pulse. The maximum likelihood estimator of the attenuated...... ultrasound pulse, which includes a maximum likelihood attenuation estimator, is derived. The results of this correspondence are of great importance for deconvolution and attenuation imaging in medical ultrasound...

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

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

    2007-04-01

    We report on the generation of nanosecond square pulses in a passively mode-locked fiber ring laser made of purely normal dispersive fibers. Different to the noise-like pulse operation of the laser, the generated square pulses are stable and have no internal structures. We show that the formation of the square pulse is due to the combined action of the pulse peak clamping effect caused by the cavity and the almost linear pulse propagation in the normal dispersive fibers.

  7. Pulse shortening of an ultrafast VECSEL

    Waldburger, D.; Alfieri, C. G. E.; Link, S. M.; Gini, E.; Golling, M.; Mangold, M.; Tilma, B. W.; Keller, U.

    2016-03-01

    Ultrafast, optically pumped, passively modelocked vertical external-cavity surface-emitting lasers (VECSELs) are excellent sources for industrial and scientific applications that benefit from compact semiconductor based high-power ultrafast lasers with gigahertz repetition rates and excellent beam quality. Applications such as self-referenced frequency combs and multi-photon imaging require sub-200-fs pulse duration combined with high pulse peak power. Here, we present a semiconductor saturable absorber mirror (SESAM) modelocked VECSEL with a pulse duration of 147 fs and 328 W of pulse peak power. The average output power was 100 mW with a repetition rate of 1.82 GHz at a center wavelength of 1034 nm. The laser has optimal beam quality operating in a fundamental transverse mode with a M2 value of average field enhancement in the QWs of ≈ 0.5 (normalized to 4 outside the structure). These results overcome the trade-off between pulse duration and peak power of the state-of-the-art threshold values of 4.35 kW peak power for a pulse duration of 400 fs and 3.3 W peak power for a pulse duration of 107 fs.

  8. Spin gymnastics with selective radiofrequency pulses

    Freeman, R.; Kupce, E. [Cambridge Univ. (United Kingdom)

    1994-12-31

    Although high resolution NMR spectra are normally excited with short intense radiofrequency pulses, there is an entire family of new experiments that can be performed with frequency-selective or ``soft`` pulses. Time-consuming two-dimensional spectroscopy may be reduced to a much shorter one-dimensional version with much finer digitization in the frequency domain. A large number of soft pulses can be combined to form a ``polychromatic pulse`` that has uniform excitation over the entire range of proton shifts except for a rejection notch at the water frequency. Polychromatic pulses can also be used to create antiphase magnetization in preparation for a coherence transfer or double-quantum experiment. An excitation profile can be designed in the form of a ``template`` that exactly matches the spectrum of a given chemical compound but has zero excitation elsewhere. This is achieved by using the information in the experimental free induction decay to construct a suitable array of soft pulses that has the required excitation pattern. In this manner, interpenetrating spectra can be separated into the spectra of the pure components, for example those of a and b glucose. Selective Hartmann-Hahn coherence transfer experiments employ similar soft pulse techniques. If several such transfers are concatenated, the method may be used as a test to see whether a group of protons is linked in an unbroken chain by scalar spin-spin interactions. (authors). 24 refs., 18 figs.

  9. SPIDER: A decade of measuring ultrashort pulses

    It was ten years ago in Rochester, New York that the first SPIDER was built. This simple acronym belies the subtleties of its inner workings; Spectral Phase Interferometry for Direct Electric-field Reconstruction (the ''f'' in field conveniently missed the cut) is a device that measures ultrashort pulses, utilizing spectral shearing interferometry and directly recovering the spectral phase. The very first SPIDER apparatus occupied nearly half an optical table, used a scanning monochromator, and had no computerized inversion routine. In the intervening decade, SPIDER has grown up. It has found a strong foothold in ultrafast laboratories throughout the world. Multiple groups have found useful new applications with this vital measurement tool, while others have contributed to the improvement of SPIDER itself, reaching to ever shorter pulses, new wavelength regimes, and making devices more sensitive, robust, smaller and faster. It also adapts to a field of research that changes rapidly. It was first designed to track and quantify the remaining spectral phase in a pulse to perfect its compression. In ten years, with the advent of pulse shapers, the real benefits of field diagnostics are becoming apparent. We have shifted away from the race towards the shortest IR pulse to a wide use of complex shaped pulses in almost every spectral range from far IR to XUV. But the quest of the shortest pulse is not over and new compression techniques utilize really broad spectra that are highly structured. All these applications provide new challenges for characterization techniques

  10. A PC based digital pulse processor

    This is the second of two papers concerning the architecture, circuitry design and performance of a pulse processing station. This multifunction system, hosted on a Personal Computer's ISA bus, incorporates a high performance Pulse Height Analyzer, a Multichannel Scaler and a Digital Pulse Processor. This paper focus on this last operation mode. The Digital Pulse Processor is mainly based on a floating point digital signal processor, TMS320C31, on a 100 MSPS dash ADC, AD9012, and on a trigger and pulse locator mechanism based on a 16-bit counter synchronized with the sample clock. The preamplifier output is directly sampled and digitized and the incoming pulses are processed in real-time with reduced dead time. The implementation of the pulse processor is discussed and some preliminary results obtained with a HPGe detector are presented. The system is fully controlled by a Windows 95 / NT user friendly software package built around the client-server model. It enables remote data assessment and system configuration in a network environment

  11. Spin gymnastics with selective radiofrequency pulses

    Although high resolution NMR spectra are normally excited with short intense radiofrequency pulses, there is an entire family of new experiments that can be performed with frequency-selective or ''soft'' pulses. Time-consuming two-dimensional spectroscopy may be reduced to a much shorter one-dimensional version with much finer digitization in the frequency domain. A large number of soft pulses can be combined to form a ''polychromatic pulse'' that has uniform excitation over the entire range of proton shifts except for a rejection notch at the water frequency. Polychromatic pulses can also be used to create antiphase magnetization in preparation for a coherence transfer or double-quantum experiment. An excitation profile can be designed in the form of a ''template'' that exactly matches the spectrum of a given chemical compound but has zero excitation elsewhere. This is achieved by using the information in the experimental free induction decay to construct a suitable array of soft pulses that has the required excitation pattern. In this manner, interpenetrating spectra can be separated into the spectra of the pure components, for example those of a and b glucose. Selective Hartmann-Hahn coherence transfer experiments employ similar soft pulse techniques. If several such transfers are concatenated, the method may be used as a test to see whether a group of protons is linked in an unbroken chain by scalar spin-spin interactions. (authors). 24 refs., 18 figs

  12. Detection of irradiated pulses by PSL method

    Photostimulated luminescence (PSL) as a screening method is very simple and rapid to detect irradiated foods but various disadvantages (light induced fading of PSL signal or response to clean foods with minerals insensitive to PSL measurement). In this study the characteristics of radiation induced PSL for 10 kinds of pulses (Chinese Soybean and Adzuki bean, Pinto bean, Cowpea, Green gram, Canadian Blue pea and Soybean, American Black-eyed pea and Chickpea, Red Kidney Bean) were investigated. The screening-PSL (s-PSL) cumulate counts of pulses significantly increased with irradiation dose up to 3 kGy. The s-PSL cumulate counts of irradiated pulses gradually decreased with increasing storage periods. The s-PSL cumulate counts of all pulse samples irradiated at a minimum dose of 0.5kGy exceeded considerably the upper screening threshold (5000 counts) regardless of storage period. Calibrated PSL (Cal-PSL) were obtained by re-irradiating the pulse samples with a gamma ray dose of 1 kGy and the PSL ratios (s-PSL/Cal-PSL) were calculated for normalization of sensitivity of the pulse samples. The PSL ratio at each irradiation dose was almost similar regardless of kind of pulses. (author)

  13. Experimental study on double-pulse laser ablation of steel upon multiple parallel-polarized ultrashort-pulse irradiations

    Schille, Joerg; Schneider, Lutz; Kraft, Sebastian; Hartwig, Lars; Loeschner, Udo

    2016-07-01

    In this paper, double-pulse laser processing is experimentally studied with the aim to explore the influence of ultrashort pulses with very short time intervals on ablation efficiency and quality. For this, sequences of 50 double pulses of varied energy and inter-pulse delay, as adjusted between 400 fs and 18 ns by splitting the laser beam into two optical paths of different length, were irradiated to technical-grade stainless steel. The depth and the volume of the craters produced were measured in order to evaluate the efficiency of the ablation process; the crater quality was analyzed by SEM micrographs. The results obtained were compared with craters produced with sequences of 50 single pulses and energies equal to the double pulse. It is demonstrated that double-pulse processing cannot exceed the ablation efficiency of single pulses of optimal fluence, but the ablation crater surface formed smoother if inter-pulse delay was in the range between 10 ns and 18 ns. In addition, the influence of pulse duration and energy distribution between the individual pulses of the double pulse on ablation was studied. For very short inter-pulse delay, no significant effect of energy variation within the double pulse on removal rate was found, indicating that the double pulse acts as a big single pulse of equal energy. Further, the higher removal efficiency was achieved when double-pulse processing using femtosecond pulses instead of picosecond pulses.

  14. XFEL/Short Pulse Science

    Schneider, Jochen

    2005-01-01

    X-rays are a most powerful tool for 3 dimensional imaging of matter on length scales from mm to nanometer. They allow for highly accurate determination of the position of atoms and their correlated motion in samples with complex structure under extreme temperature or pressure condi-tions, they probe either bulk or surface properties including order-disorder phenomena. With high resolution spectro-microscopy electronic properties of inhomogeneous novel materials are studied in great detail. So far equilibrium states are investigated. The logical next step is to extend our methodology to include the investigation of non-equilibrium, of new states of matter with atomic resolution in space and time. The XFELs provide the necessary very intense flashes of X-rays with wave-lengths down to 0.1 nm with pulse durations of 10 or 100 femtoseconds. Examples of the sug-gested applications of XFELs will be presented. Strategies for performing experiments at LINAC driven light sources will be discussed with emphasis on the ...

  15. 34 GHz pulsed magnicon project

    A high efficiency, high power magnicon amplifier at 34.272 GHz has been designed as a radiation source to drive a multi-TeV electron-positron linear collider. Simulations predict a peak output power of 45 MW in a 1.5 microsecond pulse with an efficiency of 45% and a gain of 55 dB. The amplifier is a frequency tripler, or third harmonic amplifier, in that the output frequency of 34.272 GHz is three times the input drive frequency of 11.424 GHz. Thus the rotating TM110 modes in the drive cavity, 3 gain cavities and 2 penultimate cavities are resonant near 11.424 GHz; and the rotating TM310 mode in the output cavity is resonant at 34.272 GHz. A 500 kV, 215 A high area compression electron gun will provide an electron beam with a diameter less then 1 mm. A superconducting solenoid magnet will provide a magnetic field of 13 kG in the deflection system and 23 kG in the output cavity. Simulation results for the operation of the entire magnicon amplifier (gun, magnetic system, RF system and collector) will be given, and the status described of critical hardware components

  16. Technology of Pulse Power Capacitors

    Qin, Shanshan

    Polymer film of pulse discharge capacitors operated at high repetition rate dissipates substantial power. The thermal conductivity of biaxially oriented polypropylene (BOPP) is measured as a function of metallization resistivity. The thermal conductivity in the plane of the film is about twice that of bulk polypropylene. Thermal design is optimized based on the measurement for large capacitors with multiple windings in a container. High discharge speed results in high current density at the wire arc sprayed end connections which tend to deteriorate gradually, resulting in capacitor failure during operation. To assure the end connection quality before assembly, a test procedure and apparatus for end connection integrity was developed based on monitoring the partial discharge pattern from end connection during discharge. The mechanism of clearing is analyzed which shows arc extinguishes due to the increased arc length and reduced energy so that capacitor can function normally after breakdown. In the case of a clearing discharge, the power dissipation appears to increase with time, although this is not a feature of previous models. Submicrosecond discharge requires minimizing inductance which can be achieved by optimizing the winding structure so that submicrosecond discharge becomes practical. An analysis of the inductance of multisection, very high voltage capacitors is carried out, which identifies low inductance structures for this type of capacitor.

  17. Beamlet pulsed-power system

    Larson, D.

    1996-06-01

    The 13-MJ Beamlet pulsed-power system provides power to the 512 flash lamps in the cavity and booster amplifiers. Since the flash lamps pump all of the apertures in the 2 x 2 amplifier array, the capacitor bank provides roughly four times the energy required to pump the single active beam line. During the 40 s prior to the shot, the capacitors are charged by constant-current power supplies. Ignitron switches transfer the capacitor energy to the flash lamps via coaxial cables. A preionization system triggers the flash lamps and delivers roughly 1 % of the capacitor energy 200 {mu}s prior to the main discharge. This is the first time flash-lamp preionization has been used in a large facility. Preionization improves the amplifier efficiency by roughly 5% and increases the lifetime of the flash lamps. LabVIEW control panels provide an operator interface with the modular controls and diagnostics. To improve the reliability of the system, high-energy-density, self-healing, metallized dielectric capacitors are used. High-frequency, voltage-regulated switching power supplies are integrated into each module on Beamlet, allowing greater independence among the modules and improved charge voltage accuracy, flexibility, and repeatability.

  18. Intense Pulsed Heavy Ion Beam Technology

    Masugata, Katsumi; Ito, Hiroaki

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

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

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

  20. Modulated pulse bathymetric lidar Monte Carlo simulation

    Luo, Tao; Wang, Yabo; Wang, Rong; Du, Peng; Min, Xia

    2015-10-01

    A typical modulated pulse bathymetric lidar system is investigated by simulation using a modulated pulse lidar simulation system. In the simulation, the return signal is generated by Monte Carlo method with modulated pulse propagation model and processed by mathematical tools like cross-correlation and digital filter. Computer simulation results incorporating the modulation detection scheme reveal a significant suppression of the water backscattering signal and corresponding target contrast enhancement. More simulation experiments are performed with various modulation and reception variables to investigate the effect of them on the bathymetric system performance.

  1. Pulse Compression Technique of Radio Fuze

    HU Xiu-juan; DENG Jia-hao; SANG Hui-ping

    2006-01-01

    The advantages of using phase-coded pulse compression technique for radio fuze systems are evaluated. With building mathematical models a matched filter has be en implemented successfully. Various simulations for pulse compression waveform coding were done to evaluate the performance of fuze system under noisy environment. The results of the simulation and the data analysis show that the phase-coded pulse compression gets a good result in the signal identification of the radio fuze with matched filter. Simultaneously, a suitable sidelobe suppression filter is established by simulation, the suppressed sidelobe level is acceptable to radio fuze application.

  2. Wuhan pulsed high magnetic field center

    Li, Liang; Peng, Tao; Ding, Honfa; Han, Xiaotao; Ding, Tonghai; Chen, Jin; Wang, Junfeng; Xie, Jianfeng; Wang, Shaoliang; Duan, Xianzhong; Wang, Cheng; Herlach, Fritz; Vanacken, Johan; Pan, Yuan

    2008-01-01

    Wuhan pulsed high magnetic field facility is under development. Magnets of bore sizes from 12 to 34 mm with the peak field in the range of 50 to 80 T have been designed. The pulsed power supplies consists of a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. A prototype 1 MJ, 25 kV capacitor bank is under construction. Five magnets wound with CuNb wire and copper wire reinforced internally with Zylon fiber composites and externally with stainless steel shells have be...

  3. From reactors to long pulse sources

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

  4. Electron trajectories in pulsed radiation fields

    The work reported here analyzes the dynamical behavior of an electron, initially at rest, when subjected to a radiation pulse of arbitrary, but integrable, shape. This is done by a general integration procedure that has been programmed in VAXIMA. Upon choosing a specific shape for the pulse, VAXIMA finds both the space-time trajectory and the four-momentum of the electron. These are obtained in analytic or numerical form - or both - at the choice of the user. Several examples of analytical and numerical solutions, for different pulse shapes, are given

  5. Pulse propagation in the laser wakefield accelerator

    A high-density regime of the laser wakefield accelerator is reviewed in which enhanced acceleration is achieved via resonant self-modulation of the laser pulse. This requires laser power in excess of the critical power for optical guiding and a plasma wavelength short compared to the laser pulse-length. The evolution of the laser pulse is described, including a discussion of self-modulation and laser-hose instabilities. Examples of self-modulated laser wakefield accelerators are presented. copyright 1996 American Institute of Physics

  6. Laser pulse shaping for high gradient accelerators

    Villa, F.; Anania, M. P.; Bellaveglia, M.; Bisesto, F.; Chiadroni, E.; Cianchi, A.; Curcio, A.; Galletti, M.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Gatti, G.; Moreno, M.; Petrarca, M.; Pompili, R.; Vaccarezza, C.

    2016-09-01

    In many high gradient accelerator schemes, i.e. with plasma or dielectric wakefield induced by particles, many electron pulses are required to drive the acceleration of one of them. Those electron bunches, that generally should have very short duration and low emittance, can be generated in photoinjectors driven by a train of laser pulses coming inside the same RF bucket. We present the system used to shape and characterize the laser pulses used in multibunch operations at Sparc_lab. Our system gives us control over the main parameter useful to produce a train of up to five high brightness bunches with tailored intensity and time distribution.

  7. Dynamics of pulsed plate extraction columns

    Methods of correlating holdup measurements in pulsed plate columns are reviewed and the use of the droplet characteristic velocity concept is demonstrated using published holdup data determined in the absence of mass transfer. The measurements are well correlated with the phase flowrates and pulse velocity. This is capable of modelling holdup characteristics within the accuracy of currently available data. The form of the dependence of the characteristic velocity upon pulse velocity would appear to be governed by the physical properties of the system and possibly also by the material of construction of the sieve plates. If this is subsequently confirmed, the implications will be significant in terms of column design. (author)

  8. Pulse speed on a plucked wire

    Odekirk, Tristan; Slaton, William V.

    2012-04-01

    This paper serves to update an elegant experiment published in The Physics Teacher to measure the speed of a pulse on a taut metal wire. Unfortunately, commercially available units2 that serve the same purpose are priced outside the range of most high school or college physics teaching laboratories. Wakeland et al. show how an affordable adaptation of the traditional standing wave apparatus using taut metal wire and horseshoe magnets can be used to measure the speed of a pulse by using an oscilloscope to measure an induced voltage in the wire as the pulse transverses the middle of the magnets, which are a known distance apart.

  9. Pyoderma gangrenosum treated with dexamethasone pulse therapy

    Pasricha J

    1991-01-01

    Full Text Available Three patients, with recurrent episodes of pyoderma gangrenosum, having multiple, charac-teristically large and necrotic ulcers on their extremities and/or trunk were treated with pulse therapy giving 100 mg dexamethasone in 500 ml of 5% glucose by a slow intravenous drip on 3 consecutive days. The pulses were repeated at approximately 2-week intervals. The number of pulses required to achieve complete healing in these three cases were 4, 6 and 6 respectively. There has been no recurrence in any of the cases for the last one and half years.

  10. Four-wave mixing with femtosecond pulses

    Skenderovic, H [Institute of Physics, Bijenicka cesta 46, HR-10001 Zagreb (Croatia)], E-mail: hrvoje@ifs.hr

    2009-07-15

    The recent development of noncollinear optical parametric amplifiers (NOPAs) has equipped many laboratories with widely tunable, spectrally broad ultrashort laser pulses with a duration of 15-30 fs. The present work deals with sub-20 fs pulsed degenerate four wave mixing (DFWM) on high-frequency vibrational levels in all-trans-{beta}-carotene. The observed wavepacket motion on the electronic ground state revealed fast oscillating vibrational modes whose frequencies and time development were measured. The coherent control in an open loop is demonstrated by appropriate phase shaping of the pulses.

  11. Pulsed 3-Axis Vector SERF Magnetometer

    Hedges, Morgan; Romalis, Michael

    2016-05-01

    We demonstrate a 3-axis atomic vector magnetometer operating in the SERF regime, using a single beam path, and capable of operating in Earth's field using field feedback. It has similar sensitivity along all 3 axes that is fundamentally limited by photon and atom shot noise. The scheme uses a high intensity pump pulse to polarize Rb atoms in ~ 1 μs and a sequence of magnetic field pulses applied while the atoms are monitored during free precession. The sequence used provides minimal sensitivity to pulse errors, while also allowing unambiguous discrimination between external magnetic fields and misalignment between laser and magnetic coil axes.

  12. Ultrashort X-ray pulse science

    Chin, Alan Hap [Univ. of California, Berkeley, CA (US). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    1998-05-01

    A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by 90{sup o} Thomson scattering between terawatt laser pulses and relativistic electrons. Using this technique, the author generated {approx} 300 fs, 30 keV (0.4 {angstrom}) x-ray pulses. These x-ray pulses are absolutely synchronized with ultrashort laser pulses, allowing femtosecond optical pump/x-ray probe experiments to be performed. Using the right-angle Thomson scattering x-ray source, the author performed time-resolved x-ray diffraction studies of laser-perturbated InSb. These experiments revealed a delayed onset of lattice expansion. This delay is due to the energy relaxation from a dense electron-hole plasma to the lattice. The dense electron-hole plasma first undergoes Auger recombination, which reduces the carrier concentration while maintaining energy content. Longitudinal-optic (LO) phonon emission then couples energy to the lattice. LO phonon decay into acoustic phonons, and acoustic phonon propagation then causes the growth of a thermally expanded layer. Source characterization is instrumental in utilizing ultrashort x-ray pulses in time-resolved x-ray spectroscopies. By measurement of the electron beam diameter at the generation point, the pulse duration of the Thomson scattered x-rays is determined. Analysis of the Thomson scattered x-ray beam properties also provides a novel means of electron bunch characterization. Although the pulse duration is inferred for the Thomson scattering x-ray source, direct measurement is required for other x-ray pulse sources. A method based on the laser-assisted photoelectric effect (LAPE) has

  13. Nonlinear Optics of Intense Attosecond Light Pulses

    Nazarkin, Alexander

    2006-10-01

    The interaction of an intense light pulse of "subatomic" duration with a system of multiple discrete quantum states is analyzed. The nonperturbative character of the response to the pulse field leading to an efficient conversion into high order harmonics is predicted. The spatial-temporal evolution of the field is shown to obey a generalized nonlinear wave equation of the double-sine-Gordon type. In addition to the solitary wave structures, it predicts a nontrivial regime of pulse amplification accompanied by extreme temporal self-contraction of the amplified field.

  14. Route to intense single attosecond pulses

    Tsakiris, George D.; Eidmann, Klaus; Meyer-ter-Vehn, Jürgen; Krausz, Ferenc

    2006-02-01

    A feasibility study is presented for the generation of single attosecond pulses using harmonics produced by planar targets irradiated at high intensities. The investigation focuses on the interaction of a few-optical cycles, carrier-envelope phase controlled, near-infrared laser pulse with an overdense plasma. The results obtained using an one-dimensional particle-in-cell code indicate that at laser intensities of 1020 W cm-2 a single sub-fs pulse can be generated in the 20 70 eV spectral range with an efficiency of a few per cent and with 10-3 to 10-4 for higher photon energies.

  15. Route to intense single attosecond pulses

    A feasibility study is presented for the generation of single attosecond pulses using harmonics produced by planar targets irradiated at high intensities. The investigation focuses on the interaction of a few-optical cycles, carrier-envelope phase controlled, near-infrared laser pulse with an overdense plasma. The results obtained using an one-dimensional particle-in-cell code indicate that at laser intensities of 1020 W cm-2 a single sub-fs pulse can be generated in the 20-70 eV spectral range with an efficiency of a few per cent and with 10-3 to 10-4 for higher photon energies

  16. Pulsed dc self-sustained magnetron sputtering

    The magnetron sputtering has become one of the commonly used techniques for industrial deposition of thin films and coatings due to its simplicity and reliability. At standard magnetron sputtering conditions (argon pressure of ∼0.5 Pa) inert gas particles (necessary to sustain discharge) are often entrapped in the deposited films. Inert gas contamination can be eliminated during the self-sustained magnetron sputtering (SSS) process, where the presence of the inert gas is not a necessary requirement. Moreover the SSS process that is possible due to the high degree of ionization of the sputtered material also gives a unique condition during the transport of sputtered particles to the substrate. So far it has been shown that the self-sustained mode of magnetron operation can be obtained using dc powering (dc-SSS) only. The main disadvantage of the dc-SSS process is its instability related to random arc formation. In such case the discharge has to be temporarily extinguished to prevent damaging both the magnetron source and power supply. The authors postulate that pulsed powering could protect the SSS process against arcs, similarly to reactive pulsed magnetron deposition processes of insulating thin films. To put this concept into practice, (i) the high enough plasma density has to be achieved and (ii) the type of pulsed powering has to be chosen taking plasma dynamics into account. In this article results of pulsed dc self-sustained magnetron sputtering (pulsed dc-SSS) are presented. The planar magnetron equipped with a 50 mm diameter and 6 mm thick copper target was used during the experiments. The maximum target power was about 11 kW, which corresponded to the target power density of ∼560 W/cm2. The magnetron operation was investigated as a function of pulse frequency (20-100 kHz) and pulse duty factor (50%-90%). The discharge (argon) extinction pressure level was determined for these conditions. The plasma emission spectra (400-410 nm range) and deposition

  17. High frequency and pulse scattering physical acoustics

    Pierce, Allan D

    1992-01-01

    High Frequency and Pulse Scattering investigates high frequency and pulse scattering, with emphasis on the phenomenon of echoes from objects. Geometrical and catastrophe optics methods in scattering are discussed, along with the scattering of sound pulses and the ringing of target resonances. Caustics and associated diffraction catastrophes are also examined.Comprised of two chapters, this volume begins with a detailed account of geometrically based approximation methods in scattering theory, focusing on waves transmitted through fluid and elastic scatterers and glory scattering; surface ray r

  18. Ultrashort X-ray pulse science

    A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by 90o Thomson scattering between terawatt laser pulses and relativistic electrons. Using this technique, the author generated ∼ 300 fs, 30 keV (0.4 (angstrom)) x-ray pulses. These x-ray pulses are absolutely synchronized with ultrashort laser pulses, allowing femtosecond optical pump/x-ray probe experiments to be performed. Using the right-angle Thomson scattering x-ray source, the author performed time-resolved x-ray diffraction studies of laser-perturbated InSb. These experiments revealed a delayed onset of lattice expansion. This delay is due to the energy relaxation from a dense electron-hole plasma to the lattice. The dense electron-hole plasma first undergoes Auger recombination, which reduces the carrier concentration while maintaining energy content. Longitudinal-optic (LO) phonon emission then couples energy to the lattice. LO phonon decay into acoustic phonons, and acoustic phonon propagation then causes the growth of a thermally expanded layer. Source characterization is instrumental in utilizing ultrashort x-ray pulses in time-resolved x-ray spectroscopies. By measurement of the electron beam diameter at the generation point, the pulse duration of the Thomson scattered x-rays is determined. Analysis of the Thomson scattered x-ray beam properties also provides a novel means of electron bunch characterization. Although the pulse duration is inferred for the Thomson scattering x-ray source, direct measurement is required for other x-ray pulse sources. A method based on the laser-assisted photoelectric effect (LAPE) has been

  19. Pulsed field gel electrophoresis a practical guide

    Birren, Bruce

    2014-01-01

    Pulsed Field Gel Electrophoresis: A Practical Guide is the first laboratory manual to describe the theory and practice of this technique. Based on the authors' experience developing pulsed field gel instruments and teaching procedures, this book provides everything a researcher or student needs to know in order to understand and carry out pulsed field gel experiments. Clear, well-tested protocols assume only that users have a basic familiarity with molecular biology. Thorough coverage of useful data, theory, and applications ensures that this book is also a lasting resource for more adv

  20. Analysis of multiple pulse NMR in solids

    Rhim, W.-K.; Elleman, D. D.; Vaughan, R. W.

    1973-01-01

    The general problems associated with the removal of the effects of dipolar broadening from solid-state NMR spectra are analyzed. The effects of finite pulse width and H sub 1 inhomogeneity are shown to have limited the resolution of previous pulse cycles, and a new eight-pulse cycle designed to minimize these problems is discussed. Spectra for F-19 in CaF2 taken with this cycle are presented which show residual linewidth near 10 Hz. The feasibility of measuring proton chemical shift tensors is discussed.

  1. Efficient cloning and dragging of microwave pulse into optical frequency pulse in a Doppler-broadened atomic medium

    V., Rajitha K.; Dey, Tarak N.

    2015-01-01

    The propagation of a weak optical pulse through an atomic system in closed $\\Lambda$ configuration is investigated in which the hyper fine levels are coupled by a microwave pulse. Under three photon resonance condition, it is observed that the probe pulse shape gets cloned by the shape of the microwave pulse along propagation through the medium. The temporal position of the probe pulse is dragged to that of the microwave pulse. A simple expression for the linear susceptibility of the medium f...

  2. Performance Analysis of Multiple Access 60 GHz System Using Frequency-shifted Gaussian Pulse and Non-carrier PSWF Pulse

    Hao Zhang; Wei Shi; Tingting Lu; Jingjing Wang; Xinjie Wang

    2013-01-01

    In this paper, a kind of impulse radio (IR) 60 GHz pulse based on Prolate Spheroidal Wave Functions (PSWF) is proposed. The capacity and performance for multiple access 60 GHz communication system based on carrier pulse and impulse radio pulse are analyzed separately. Both frequency-shifted Gaussian pulse and Prolate Spheroidal Wave Functions (PSWF) pulse are considered and devised according to the federal communication commission (FCC) power constraints. Pulse position modulation (PPM) with ...

  3. Fast initial continuous current pulses versus return stroke pulses in tower-initiated lightning

    Azadifar, Mohammad; Rachidi, Farhad; Rubinstein, Marcos; Rakov, Vladimir A.; Paolone, Mario; Pavanello, Davide; Metz, Stefan

    2016-06-01

    We present a study focused on pulses superimposed on the initial continuous current of upward negative discharges. The study is based on experimental data consisting of correlated lightning current waveforms recorded at the instrumented Säntis Tower in Switzerland and electric fields recorded at a distance of 14.7 km from the tower. Two different types of pulses superimposed on the initial continuous current were identified: (1) M-component-type pulses, for which the microsecond-scale electric field pulse occurs significantly earlier than the onset of the current pulse, and (2) fast pulses, for which the onset of the field matches that of the current pulse. We analyze the currents and fields associated with these fast pulses (return-stroke type (RS-type) initial continuous current (ICC) pulses) and compare their characteristics with those of return strokes. A total of nine flashes containing 44 RS-type ICC pulses and 24 return strokes were analyzed. The median current peaks associated with RS-type ICC pulses and return strokes are, respectively, 3.4 kA and 8 kA. The associated median E-field peaks normalized to 100 km are 1.5 V/m and 4.4 V/m, respectively. On the other hand, the electric field peaks versus current peaks for the two data sets (RS-type ICC pulses and return strokes) are characterized by very similar linear regression slopes, namely, 3.67 V/(m kA) for the ICC pulses and 3.77 V/(m kA) for the return strokes. Assuming the field-current relation based on the transmission line model, we estimated the apparent speed of both the RS-type ICC pulses and return strokes to be about 1.4 × 108 m/s. A strong linear correlation is observed between the E-field risetime and the current risetime for the ICC pulses, similar to the relation observed between the E-field risetime and current risetime for return strokes. The similarity of the RS-type ICC pulses with return strokes suggests that these pulses are associated with the mixed mode of charge transfer to ground.

  4. Pulse ignition characterization of mercury ion thruster hollow cathode using an improved pulse ignitor

    Wintucky, E. G.; Gruber, R. P.

    1978-01-01

    An investigation of the high voltage pulse ignition characteristics of the 8-cm mercury ion thruster neutralizer cathode identified a low rate of voltage rise and long pulse duration as desirable factors for reliable cathode starting. Cathode starting breakdown voltages were measured over a range of mercury flow rates and tip heater powers for pulses with five different rates of voltage rise. Breakdown voltage requirements for the fastest rising pulse (2.5 to 3.0 kV/microsec) were substantially higher (2 kV or more) than for the slowest rising pulse (0.3 to 0.5 kV/microsec) for the same starting conditions. The paper also describes an improved, low impedance pulse ignitor circuit which reduces power losses and eliminates problems with control and packaging associated with earlier designs.

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

    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.

  6. High gain broadband amplification of ultraviolet pulses in optical parametric chirped pulse amplifier.

    Wnuk, Paweł; Stepanenko, Yuriy; Radzewicz, Czesław

    2010-04-12

    We report on a high gain amplification of broadband ultraviolet femtosecond pulses in an optical parametric chirped pulse amplifier. Broadband ultraviolet seed pulses were obtained by an achromatic frequency doubling of the output from a femtosecond Ti:Sapphire oscillator. Stretched seed pulses were amplified in a multipass parametric amplifier with a single BBO crystal pumped by a ns frequency quadrupled Nd:YAG laser. A noncollinear configuration was used for a broadband amplification. The total (after compression) amplification of 2.510(5) was achieved, with compressed pulse energy of 30 microJ and pulse duration of 24 fs. We found that the measured gain was limited by thermal effects induced by the absorption of the pump laser by color centers created in the BBO crystal. PMID:20588633

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

    Yuan, Kai-Jun; Bandrauk, André D.

    2013-07-01

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

  8. XUV attosecond pulses: generation and measurement

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

  9. A solid state pulsed NMR spectrometer

    A 10 MHz pulsed NMR spectrometer, built using mostly solid state devices, is described. The pulse programmer provides 2-pulse, 3-pulse, saturation burst and Carr-Purcell sequences both in repetitive and manual modes of operation. The transmitter has a maximum power output of approximately 2 kW with a 75Ω output impedance termination. The total gain of the receiver system is around 120 dB with a minimum band width of 2 MHz. The recovery time of the receiver is approximately 7μsec. A two-channel boxcar integrator capable of working in the single channel, differential and double boxcar modes provides signal to noise ratio improvement. The sensitivity and the linearity of the boxcar integrator are approximately 2 mV and approximately 0.1% respectively. (auth.)

  10. Pulse radiolysis studies of model membranes

    In this thesis the influence of the structure of membranes on the processes in cell membranes were examined. Different models of the membranes were evaluated. Pulse radiolysis was used as the technique to examine the membranes. (R.B.)

  11. Ultrashort Pulse Propagation in Nonlinear Dispersive Fibers

    Agrawal, Govind P.

    Ultrashort optical pulses are often propagated through optical waveguides for a variety of applications including telecommunications and supercontinuum generation [1]. Typically the waveguide is in the form of an optical fiber but it can also be a planar waveguide. The material used to make the waveguide is often silica glass, but other materials such as silicon or chalcogenides have also been used in recent years. What is common to all such materials is they exhibit chromatic dispersion as well as the Kerr nonlinearity. The former makes the refractive index frequency dependent, whereas the latter makes it to depend on the intensity of light propagating through the medium [2]. Both of these effects become more important as optical pulses become shorter and more intense. For pulses not too short (pulse widths > 1 ns) and not too intense (peak powers fibers but similar results are expected for other waveguides made of different materials

  12. Pulse oximetry in sickle cell disease.

    Weston Smith, S G; Glass, U H; Acharya, J; Pearson, T C

    1989-01-01

    The place of pulse oximetry in monitoring arterial oxygen saturation in sickle cell disease has been evaluated. In four admissions of patients with sickle cell anaemia with varying degrees of arterial haemoglobin oxygen desaturation, pulse oximetry was compared with a simultaneous assessment of oxygen saturation by arterial blood gas measurement and oxygen dissociation curve (ODC) analysis. Close agreement was found between the oxygen saturation measured by pulse oximetry and that calculated from the measured arterial partial pressure of oxygen (PaO2) with reference to the patient's own ODC. Calculation of oxygen saturation by the blood gas analyser assuming a normal ODC was erroneous. Pulse oximetry is an accurate and effective non-invasive method for monitoring the arterial oxygen saturation in sickle cell disease. PMID:2591150

  13. The ESRF Miniature Pulsed Magnetic Field System

    van der Linden, Peter J. E. M.; Strohm, Cornelius; Roth, Thomas; Detlefs, Carsten; Mathon, Olivier

    2010-06-01

    We have developed a portable system to provide pulsed magnetic fields on the ESRF X-ray beamlines. The complete system consists of a power supply, liquid Helium and liquid Nitrogen dewars with a siphon each, control electronics and a double cryostat for separate coil and sample cooling. The liquid nitrogen cooled solenoids reach a maximum field of 30 Tesla for a total pulse duration of one milisecond. They are constructed for optimised cooling rate after the pulse to obtain a high duty cycle, the repetition rate is five pulses per minute at maximum field. The sample is cooled in an independent Helium flow cryostat which is inserted into the bore of the magnet. The flow cryostat has a temperature range from 5 to 250 Kelvin with a direct contact between the sample and Helium flow. This overview gives a general presentation of the system and we will show recent results.

  14. High frequency group pulse electrochemical machining

    WU Gaoyang; ZHANG Zhijing; ZHANG Weimin; TANG Xinglun

    2007-01-01

    In the process of machining ultrathin metal structure parts,the signal composition of high frequency group pulse,the influence of frequency to reverse current,and the design of the cathode in high frequency group pulse electrochemical machining (HGPECM) are discussed.The experiments on process were carried out.Results indicate that HGPECM can greatly improve the characteristics of the inter-electrode gap flow field,reduce electrode passivation,and obtain high machining quality.The machining quality is obviously improved by increasing the main pulse frequency.The dimensional accuracy reaches 30-40 pro and the roughness attained is at 0.30-0.35 μm.High frequency group pulse electrochemical machining can be successfully used in machining micro-parts.

  15. Fast Heat Pulse Propagation by Turbulence Spreading

    Naulin, Volker; Juul Rasmussen, Jens; Mantica, Paola;

    2009-01-01

    The propagation of a cold pulse initiated by edge cooling in JET is compared to propagation of the heat wave originating from a modulation of the heating source roughly at mid radius. It is found that the propagation of the cold pulse is by far faster than what could be predicted on the basis...... of the heat wave propagation, and within local transport models no sufficient explanation for this behaviour can be found. Recently, modelling of the cold pulse propagation using non-local effects and a transport equation that uses fractional derivatives has been successfully applied to model the effect [1...... to the core have been established [3]. Here we report on recent results in the modelling of cold pulse propagation using turbulence spreading transport models....

  16. Distortion of ultrashort pulses caused by aberrations

    Horváth, Z. L.; Kovács, A. P.; Bor, Zs.

    The effect of the primary wave aberrations (spherical aberration, astigmatism and coma) on ultrashort pulses is studied by the Nijboer-Zernike theory. The results of the geometrical and the wave optical treatments are compared.

  17. Propagating Characteristics of Pulsed Laser in Rain

    Jing Guo

    2015-01-01

    Full Text Available To understand the performance of laser ranging system under the rain weather condition, we need to know the propagating characteristics of laser pulse in rain. In this paper, the absorption and attenuation coefficients were calculated based on the scattering theories in discrete stochastic media, and the propagating characteristics of laser pulse in rain were simulated and analyzed using Monte-Carlo method. Some simulation results were verified by experiments, and the simulation results are well matched with the experimental data, with the maximal deviation not less than 7.5%. The results indicated that the propagating laser beam would be attenuated and distorted due to the scattering and absorption of raindrops, and the energy attenuation and pulse shape distortion strongly depended on the laser pulse widths.

  18. Multiphoton ionization with femtosecond laser pulses

    There are a number of reasons to use subpicosecond pulses in multiphoton ionization experiments. Pulses with shorter risetimes make it possible to study processes with higher rates before one runs into the problem of depletion of target atoms. Furthermore, the momentum of the electron does not change between the point of ionization and the detector if the pulse expires before the electron has time to sample the spatial inhomogeneity of the light intensity. This makes it possible to identify the intensity at which an electron was formed from the energy with which it reaches the detector. Yet another advantage is the fact that the primary ionization products are subject to the ionizing radiation for only a short amount of time, thus reducing the probability of sequential ionization as compared to direct processes. In this paper the experimental results on the multiphoton ionization of xenon with pulses of 100 fs, that were obtained during the preceding year at ENSTA, Palaiseau, will be presented

  19. Heat pulse propagation studies in TFTR

    Fredrickson, E.D.; Callen, J.D.; Colchin, R.J.; Efthimion, P.C.; Hill, K.W.; Izzo, R.; Mikkelsen, D.R.; Monticello, D.A.; McGuire, K.; Bell, J.D.

    1986-02-01

    The time scales for sawtooth repetition and heat pulse propagation are much longer (10's of msec) in the large tokamak TFTR than in previous, smaller tokamaks. This extended time scale coupled with more detailed diagnostics has led us to revisit the analysis of the heat pulse propagation as a method to determine the electron heat diffusivity, chi/sub e/, in the plasma. A combination of analytic and computer solutions of the electron heat diffusion equation are used to clarify previous work and develop new methods for determining chi/sub e/. Direct comparison of the predicted heat pulses with soft x-ray and ECE data indicates that the space-time evolution is diffusive. However, the chi/sub e/ determined from heat pulse propagation usually exceeds that determined from background plasma power balance considerations by a factor ranging from 2 to 10. Some hypotheses for resolving this discrepancy are discussed. 11 refs., 19 figs., 1 tab.

  20. Heat pulse propagation studies in TFTR

    The time scales for sawtooth repetition and heat pulse propagation are much longer (10's of msec) in the large tokamak TFTR than in previous, smaller tokamaks. This extended time scale coupled with more detailed diagnostics has led us to revisit the analysis of the heat pulse propagation as a method to determine the electron heat diffusivity, chi/sub e/, in the plasma. A combination of analytic and computer solutions of the electron heat diffusion equation are used to clarify previous work and develop new methods for determining chi/sub e/. Direct comparison of the predicted heat pulses with soft x-ray and ECE data indicates that the space-time evolution is diffusive. However, the chi/sub e/ determined from heat pulse propagation usually exceeds that determined from background plasma power balance considerations by a factor ranging from 2 to 10. Some hypotheses for resolving this discrepancy are discussed. 11 refs., 19 figs., 1 tab

  1. Pulse transformer for GaAs laser

    Rutz, E. M.

    1976-01-01

    High-radiance gallium arsenide (GaAs) laser operating at room temperature is utilized in optical navigation system. For efficient transformer-to-laser impedance match, laser should be connected directly to pulse transformer secondary winding.

  2. Investigations on the pulse operation of YAYOI

    This report is composed of ten independent documents concerning the pulse operation of YAYOI, which were prepared in the period between July, 1976, and March, 1977. The titles of the documents included in this report are: (1) the operational sequence of the linac neutron generating facility, (2) safety systems of linac pulse operation and the treatment and preservation of neutron generating targets, (3) nuclear calculation concerning linac pulse operation, (4) simulated natural uranium core, (5) linac neutron target system, (6) computer processing accompanying linac pulse operation, (7) fundamental concept of electron beam generation within the reactor room, (8) reactor room shielding requirements for the linac neutron source, (9) TOF measuring room, and (10) utilization of low energy neutrons from P-YAYOI operation. (Aoki, K.)

  3. Optical quality of pulsed aerodynamic laser windows

    The feasibility of using a shock tube-generated pulsed flow field as a single-shot window for short, high-energy laser pulses is investigated, with a view to single pulse gas laser-driven, inertial confinement fusion facility application. A scribed diaphragm shock tube with glass endwalls was used to simulate the window, and a ruby laser pulse was transmitted along the tube axis after the diaphragm burst. Pressure wave field optical quality and turbulent contact interface were recorded holographically at different delay times for a variety of pressures and gas compositions in the driver and driven sections of the shock tube. Interferograms were interpreted by means of digital techniques to determine beam-quality degradations, and showed that a beam quality of 1.33, adequate for laser fusion use, was routinely obtainable at the ruby laser wavelength

  4. Beam pulse length determination by spectral analysis

    The report discusses the feasibility of identifying the beam pulse length for heavy ion beams down to 10 enA by observing the amplitude of the Fourier components of the beam pulse train on commercially available UHF spectrum analyzers. Two cases are investigated: 1) where the beam is intercepted by a coaxial Faraday Cup. The resulting electrical signal represents the beam current in the time domain Max signal-to-noise ratio results from entire collection of the beam and 2) where the beam induces a signal in a loosely-coupled capacitive pick-up. The induced pulse train waveform is correspondingly altered and signal-to-noise ratio deteriates. Both cases are shown to be beyond the limits of practical spectrum analyzers for 10 enA beams when 60 pulse widths are considered

  5. Binary Pulse Compression Techniques for MST Radars

    Woodman, R. F.; Sulzer, M. P.; Farley, D. T.

    1984-01-01

    In most mesosphere-stratosphere-troposphere (MST) applications pulsed radars are peak power limited and have excess average power capability. Short pulses are required for good range resolution but the problem of range biguity (signals received simultaneously from more than one altitude) sets a minimum limit on the interpulse period (IPP). Pulse compression is a echnique which allows more of the transmitter average power capacity to be used without scarificing range resolution. Binary phase coding methods for pulse compression are discussed. Many aspects of codes and decoding and their applications to MST experiments are addressed; this includes Barker codes and longer individual codes, and then complementary codes and other code sets. Software decoding, hardware decoders, and coherent integrators are also discussed.

  6. Heat accumulation during pulsed laser materials processing.

    Weber, Rudolf; Graf, Thomas; Berger, Peter; Onuseit, Volkher; Wiedenmann, Margit; Freitag, Christian; Feuer, Anne

    2014-05-01

    Laser materials processing with ultra-short pulses allows very precise and high quality results with a minimum extent of the thermally affected zone. However, with increasing average laser power and repetition rates the so-called heat accumulation effect becomes a considerable issue. The following discussion presents a comprehensive analytical treatment of multi-pulse processing and reveals the basic mechanisms of heat accumulation and its consequence for the resulting processing quality. The theoretical findings can explain the experimental results achieved when drilling microholes in CrNi-steel and for cutting of CFRP. As a consequence of the presented considerations, an estimate for the maximum applicable average power for ultra-shorts pulsed laser materials processing for a given pulse repetition rate is derived. PMID:24921828

  7. Sound pulse broadening in stressed granular media.

    Langlois, Vincent; Jia, Xiaoping

    2015-02-01

    The pulse broadening and decay of coherent sound waves propagating in disordered granular media are investigated. We find that the pulse width of these compressional waves is broadened when the disorder is increased by mixing the beads made of different materials. To identify the responsible mechanism for the pulse broadening, we also perform the acoustic attenuation measurement by spectral analysis and the numerical simulation of pulsed sound wave propagation along one-dimensional disordered elastic chains. The qualitative agreement between experiment and simulation reveals a dominant mechanism by scattering attenuation at the high-frequency range, which is consistent with theoretical models of sound wave scattering in strongly random media via a correlation length. PMID:25768496

  8. Pulse radiolysis facilities and activities in Japan

    Pulse radiolysis studies in Japan have been reviewed in special reference to the facilities and the people who have engaged in the experiments. Main achievement is summarized with the list of selected publications. (author)

  9. Development of recirculating RF pulse compression system

    An RF pulse compression technique using recirculating resonant cavity is under development for accelerating energy reinforcement for KEK B-factory. Cavity design and fabrication of cold model are described. (author)

  10. High velocity pulsed wire-arc spray

    Witherspoon, F. Douglas (Inventor); Massey, Dennis W. (Inventor); Kincaid, Russell W. (Inventor)

    1999-01-01

    Wire arc spraying using repetitively pulsed, high temperature gas jets, usually referred to as plasma jets, and generated by capillary discharges, substantially increases the velocity of atomized and entrained molten droplets. The quality of coatings produced is improved by increasing the velocity with which coating particles impact the coated surface. The effectiveness of wire-arc spraying is improved by replacing the usual atomizing air stream with a rapidly pulsed high velocity plasma jet. Pulsed power provides higher coating particle velocities leading to improved coatings. 50 micron aluminum droplets with velocities of 1500 m/s are produced. Pulsed plasma jet spraying provides the means to coat the insides of pipes, tubes, and engine block cylinders with very high velocity droplet impact.

  11. Modeling Pulse Characteristics in Xenon with NEST

    Mock, Jeremy; Kazkaz, Kareem; Szydagis, Matthew; Tripathi, Mani; Uvarov, Sergey; Woods, Michael; Walsh, Nicholas

    2013-01-01

    A comprehensive model for describing the characteristics of pulsed signals, generated by particle interactions in xenon detectors, is presented. An emphasis is laid on two-phase time projection chambers, but the models presented are also applicable to single phase detectors. In order to simulate the pulse shape due to primary scintillation light, effects such as the ratio of singlet and triplet dimer state populations, as well as their corresponding decay times, and the recombination time are incorporated into the model. In a two phase time projection chamber, when simulating the pulse caused by electroluminescence light, parameters such as ionization electron mean free path in gas, the drift velocity, singlet and triplet decay times, diffusion constants, and the electron trapping time, have been implemented. This modeling has been incorporated into a complete software package, which realistically simulates the expected pulse shapes for these types of detectors.

  12. Modeling pulse characteristics in Xenon with NEST

    Mock, J.; Barry, N.; Kazkaz, K.; Stolp, D.; Szydagis, M.; Tripathi, M.; Uvarov, S.; Woods, M.; Walsh, N.

    2014-04-01

    A comprehensive model for describing the characteristics of pulsed signals, generated by particle interactions in xenon detectors, is presented. An emphasis is laid on two-phase time projection chambers, but the models presented are also applicable to single phase detectors. In order to simulate the pulse shape due to primary scintillation light, the effects of the ratio of singlet and triplet dimer state populations, as well as their corresponding decay times, and the recombination time are incorporated into the model. In a two phase time projection chamber, when simulating the pulse caused by electroluminescence light, the ionization electron mean free path in gas, the drift velocity, singlet and triplet decay times, diffusion constants, and the electron trapping time, have been implemented. This modeling has been incorporated into a complete software package, which realistically simulates the expected pulse shapes for these types of detectors.

  13. Resonant entrainment of a confined pulsed jet

    Parikh, P. G.; Moffat, R. J.

    1982-01-01

    This paper reports the discovery of a new resonant entrainment phenomenon associated with a confined, pulsed jet flow. It was found that a confined jet, when pulsed at an organ-pipe resonant frequency of the confinement tube, experiences greatly enhanced entrainment and mixing near the exit end of the confinement tube compared to a steady confined jet. The mixing and entrainment rates for the resonantly pulsed confined jet approach, and in some cases slightly exceed, those for an unconfined pulsed jet. Both visual and quantitative evidence of this phenomenon is presented. The new effect should be of considerable interest in ejector and combustor design, both of which benefit from any enhancement in mixing between a primary and a secondary flow

  14. Current Pulses Momentarily Enhance Thermoelectric Cooling

    Snyder, G. Jeffrey; Fleurial, Jean-Pierre; Caillat, Thierry; Chen, Gang; Yang, Rong Gui

    2004-01-01

    The rates of cooling afforded by thermoelectric (Peltier) devices can be increased for short times by applying pulses of electric current greater than the currents that yield maximum steady-state cooling. It has been proposed to utilize such momentary enhancements of cooling in applications in which diode lasers and other semiconductor devices are required to operate for times of the order of milliseconds at temperatures too low to be easily obtainable in the steady state. In a typical contemplated application, a semiconductor device would be in contact with the final (coldest) somewhat taller stage of a multistage thermoelectric cooler. Steady current would be applied to the stages to produce steady cooling. Pulsed current would then be applied, enhancing the cooling of the top stage momentarily. The principles of operation are straightforward: In a thermoelectric device, the cooling occurs only at a junction at one end of the thermoelectric legs, at a rate proportional to the applied current. However, Joule heating occurs throughout the device at a rate proportional to the current squared. Hence, in the steady state, the steady temperature difference that the device can sustain increases with current only to the point beyond which the Joule heating dominates. If a pulse of current greater than the optimum current (the current for maximum steady cooling) is applied, then the junction becomes momentarily cooled below its lowest steady temperature until thermal conduction brings the resulting pulse of Joule heat to the junction and thereby heats the junction above its lowest steady temperature. A theoretical and experimental study of such transient thermoelectric cooling followed by transient Joule heating in response to current pulses has been performed. The figure presents results from one of the experiments. The study established the essential parameters that characterize the pulse cooling effect, including the minimum temperature achieved, the maximum

  15. Efficient pulsed CO2 laser calculations

    Stone, David H.; Honey, David A.

    1991-02-01

    A computationally efficient scheme for generating pumping rates was developed for use with a pulsed CO2 laser model. A steady-state solution of the Boltzmann electron transport equation generates the rates. Vibrational temperatures for the CO2 and N2 populations are determined by iterating the Boltzmann solver with the rate equation model. Rapid convergence and coarse grids allow quick calculations of pulse shape, peak power, and total energy. Results compare well with a fully time-dependent Boltzmann solver.

  16. Long pulse operation on Tore Supra

    Monier-Garbet, P

    2004-07-01

    This document gathers a series of transparencies dedicated to the long pulse operation on Tore-Supra. The structure of the document is described as follows: the first part is an introduction recalling fusion basis and presenting the different physical and technological phenomenon time scales. The second part is dedicated to the production of long pulses through non-inductive drive and some experimental scenarios illustrate it. The final part is devoted to physics issues like particle retention.

  17. Long pulse operation on Tore Supra

    This document gathers a series of transparencies dedicated to the long pulse operation on Tore-Supra. The structure of the document is described as follows: the first part is an introduction recalling fusion basis and presenting the different physical and technological phenomenon time scales. The second part is dedicated to the production of long pulses through non-inductive drive and some experimental scenarios illustrate it. The final part is devoted to physics issues like particle retention

  18. Interferometry of light propagation in pulsed fields

    Dobrich, Babette; Gies, Holger

    2009-01-01

    We investigate the use of ground-based gravitational-wave interferometers for studies of the strong-field domain of QED. Interferometric measurements of phase velocity shifts induced by quantum fluctuations in magnetic fields can become a sensitive probe for nonlinear self-interactions among macroscopic electromagnetic fields. We identify pulsed magnets as a suitable strong-field source, since their pulse frequency can be matched perfectly with the domain of highest sensitivity of gravitation...

  19. Pulsed reactor IBR-2 in the 'nineties

    One may expect that in the 1990s a considerable part of neutron scattering experiments will be carried out on pulsed neutron sources. Pulsed reactors of the IBR-type are the founders of a family of pulsed sources of thermal neutrons. The first IBR-type reactor started operation in 1960 with a mean thermal power of 1 kW. In 1984 the IBR-2 reactor had a mean power of 2 MW, a pulsed power of 1500 MW at 5 s-1 repetition rate and a power pulse duration of 215 μs. The peak leakage current of thermal neutrons from the moderator surface reached 1x1016n.cm-2.s-1 which allows on the sample a mean flux of thermal neutrons up to 5x107n.cm-2.s-1 monochromized by the time-of-flight method with an uncertainty of Δdelta approx.= 0.02 A. The achieved parameters, being reasonably good for a wide range of experiments, are not to be considered as being a technical limit for this type of pulsed neutron source. The experience we already have allows us to expect development in the following directions: increasing of the reactor mean power, shortening of the pulse duration, installation of the liquid hydrogen moderator. The IBR-2 reactor is used in four main fields: physics of condensed matter, nuclear physics, fundamental and applied physics. The greatest activity is in condensed matter research. In addition to conventional structural and dynamic studies we intend to expand investigations to kinetics of transitions in the time range up to 10-4s (time-resolved spectroscopy), properties of short-living non-equilibrium states, properties of matter under extreme conditions created in the pulsed mode (e.g. under the influence of superstrong magnetic fields). We expect that within the next decade, neutron methods will be increasingly introduced into different areas of research and technology. (author)

  20. Attosecond pulse shaping using partial phase matching

    Austin, Dane R.; Biegert, Jens

    2014-01-01

    We propose a method for programmable shaping of the amplitude and phase of the XUV and x-ray attosecond pulses produced by high-order harmonic generation. It overcomes the bandwidth limitations of existing spectral filters and enables removal of the intrinsic attosecond chirp as well as the synthesis of pulse sequences. It is based on partial phase matching, such as quasi-phase matching, using a longitudinally addressable modulation.

  1. Ultrashort pulsed laser technology development program

    Manke, Gerald C.

    2014-10-01

    The Department of Navy has been pursuing a technology development program for advanced, all-fiber, Ultra Short Pulsed Laser (USPL) systems via Small Business Innovative Research (SBIR) programs. Multiple topics have been published to promote and fund research that encompasses every critical component of a standard USPL system and enable the demonstration of mJ/pulse class systems with an all fiber architecture. This presentation will summarize published topics and funded programs.

  2. Applications of Pulse-Coupled Neural Networks

    Ma, Yide; Wang, Zhaobin

    2011-01-01

    "Applications of Pulse-Coupled Neural Networks" explores the fields of image processing, including image filtering, image segmentation, image fusion, image coding, image retrieval, and biometric recognition, and the role of pulse-coupled neural networks in these fields. This book is intended for researchers and graduate students in artificial intelligence, pattern recognition, electronic engineering, and computer science. Prof. Yide Ma conducts research on intelligent information processing, biomedical image processing, and embedded system development at the School of Information Sci

  3. Pulsed uv nitrogen laser: dynamical behavior

    Using the time dependent rate equations, the dynamical behavior of a high power pulsed N2 laser radiating at 337.1 nm is derived. The threshold conditions are given. The output peak power and pulse width as a function of length and initial inversion density are shown. The theoretical results derived are compared with experimental data and are found to be in good agreement

  4. Propagation of Partial Discharge Pulses in Winding

    Karel Zalis

    2004-01-01

    A lot of measurements of the attenuation of partial discharge pulses on the model of winding was realized in the High Voltage Laboratory of the Czech Technical University in Prague. Current pulses from a charge calibrator were injected into different parts of winding and both the distortion of the charge and their deformations at the end terminals were observed and evaluated. It was confirmed that the apparent charge of a partial discharge, as a diagnostic parameter, is not relativel...

  5. Space-time engineering with LASETRON pulses

    Kozlowski, M.; Marciak-Kozlowska, J.

    2003-01-01

    The LASETRON project (Phys. Rev. Lett, 88, (2002), p. 074801-1) offers the possibility of the investigation of electron-positron structure of the space-time. Following our results (From Quarks to Bulk Matter, Hadronic Press, 2001) we analyze theoretically possibility of the penetration of zeptosecond laser pulses through space-time. Key words: Zeptosecond laser pulses; LASETRON; Electron-positron pairs; Space-time.

  6. The Dynamics of Compact Laser Pulses

    Goto, S; Tucker, Robin William; Walton, T. J.

    2015-01-01

    We discuss the use of a class of exact finite energy solutions to the vacuum source-free Maxwell equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged point particles. These compact solutions are classified in terms of their chiral content and their influence on particular charge configurations in space. The results of such classical interactions motivate a phenomenological quantum description of a propagating laser pulse in a medium i...

  7. The dynamics of compact laser pulses

    Goto, S.; Tucker, R. W.; Walton, T. J.

    2016-07-01

    We discuss the use of a class of exact finite energy solutions to the vacuum source-free Maxwell equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged point particles. These compact solutions are classified in terms of their chiral content and their influence on particular charge configurations in space. The results of such classical interactions motivate a phenomenological quantum description of a propagating laser pulse in a medium in terms of an effective quantum Hamiltonian.

  8. Pulsed liquid microjet for microsurgical applications

    Palanker, Daniel V.; Fletcher, Daniel A.

    2001-05-01

    The precision of soft tissue dissection with pulsed lasers in endo-microsurgery is typically limited by collateral damage from vapor bubbles created during energy deposition. Expansion and collapse of the cavitation bubble introduces collateral damage extending far beyond the primary energy deposition zone in both, axial and radial directions. We present an alternative technique that allows for creating of only axial pulsed liquid flow with well-defined radial dimensions and axial velocity.

  9. FEU-140 photomultipliers in pulsed plasma spectroscopy

    Special fast photomultipliers are usually employed in photoelectric spectroscopy of nonstationary plasmas. Measurements have been made on the pulse characteristics and spectral sensitivity for the FEU-140 photomultiplier, which enables one to record a light flux of about 10-10 W as pulses of duration down to 10 nsec in the range 200-650 nm with a fairly wide linearity range (10-10-10-18 W)

  10. Cold moderators for pulsed neutron sources

    This paper reviews cold moderators in pulsed sources and provides details of the performance of different cold moderator materials and configurations. Analytical forms are presented which describe wavelength spectra and emission time distributions. Several types of cooling arrangements used in pulsed moderators are described. Choices of materials are surveyed. The author examines some of the radiation damage effects in cold moderators, including the phenomenon of burping in irradiated cold solid methane

  11. Cold moderators for pulsed neutron sources

    This paper reviews cold moderators in pulsed neutron sources and provides details of the performance of different cold moderator materials and configurations. Analytical forms are presented which describe wavelength spectra and emission time distributions. Several types of cooling arrangements used in pulsed source moderators are described. Choices of materials are surveyed. The author examines some of the radiation damage effects in cold moderators, including the phenomenon of ''burping'' in irradiated cold solid methane. 9 refs., 15 figs., 4 tabs

  12. Mathematical description of bacterial traveling pulses

    Bournaveas, Nikolaos; Buguin, Axel; Calvez, Vincent; Perthame, Benoît; Saragosti, Jonathan; Silberzan, Pascal

    2009-01-01

    The Keller-Segel system has been widely proposed as a model for bacterial waves driven by chemotactic processes. Current experiments on {\\em E. coli} have shown precise structure of traveling pulses. We present here an alternative mathematical description of traveling pulses at a macroscopic scale. This modeling task is complemented with numerical simulations in accordance with the experimental observations. Our model is derived from an accurate kinetic description of the mesoscopic run-and-t...

  13. Mathematical Description of Bacterial Traveling Pulses

    Saragosti, Jonathan; Calvez, Vincent; Bournaveas, Nikolaos; Buguin, Axel; Silberzan, Pascal; Perthame, Benoît

    2010-01-01

    The Keller-Segel system has been widely proposed as a model for bacterial waves driven by chemotactic processes. Current experiments on Escherichia coli have shown the precise structure of traveling pulses. We present here an alternative mathematical description of traveling pulses at the macroscopic scale. This modeling task is complemented with numerical simulations in accordance with the experimental observations. Our model is derived from an accurate kinetic description of the mesoscopic ...

  14. Mathematical description of bacterial traveling pulses

    Bournaveas, Nikolaos; Buguin, Axel; Calvez, Vincent; Perthame, Benoît; Saragosti, Jonathan; Silberzan, Pascal

    2010-01-01

    The Keller-Segel system has been widely proposed as a model for bacterial waves driven by chemotactic processes. Current experiments on E. coli have shown precise structure of traveling pulses. We present here an alternative mathematical description of traveling pulses at a macroscopic scale. This modeling task is complemented with numerical simulations in accordance with the experimental observations. Our model is derived from an accurate kinetic description of the mesoscopic run-and-tumble ...

  15. Double regenerative amplification of picosecond pulses

    Bai, Zhen-ao; Chen, Li-yuan; Bai, Zhen-xu; Chen, Meng; Li, Gang

    2012-04-01

    An double Nd:YAG regenerative amplification picosecond pulse laser is demonstrated under the semiconductor saturable absorption mirror(SESAM) mode-locking technology and regenerative amplification technology, using BBO crystal as PC electro-optic crystal. The laser obtained is 20.71ps pulse width at 10 KHz repetition rate, and the energy power is up to 4W which is much larger than the system without pre-amplification. This result will lay a foundation for the following amplification.

  16. Laser pulse shaping with liquid crystals

    Martín Pereda, José Antonio; Muriel Fernández, Miguel Ángel

    1983-01-01

    A method of unpolarized laser pulses shaping is reported. The basis of the method is the use of an hybrid optical bistable device with nematic liquid-crystals, similar to the one previously reported by us. A sample of the input light constrols, by an asymmetrical electronic comparator, a 1 x 2 electro-optical total switch. The output pulses are reshaped and maintain the same polarization properties as the input light. From triangular input light signals, symmetriacl and asymmetrical output pu...

  17. Steady State versus Pulsed Tokamak DEMO

    Full text: The present report deals with a Review of problems for a Steady state(SS) DEMO, related argument is treated about the models and the present status of comparison between the characteristics of DEMO pulsed versus a Steady state device.The studied SS DEMO Models (SLIM CS, PPCS model C EU-DEMO, ARIES-RS) are analyzed from the point of view of the similarity scaling laws and critical issues for a steady state DEMO. A comparison between steady state and pulsed DEMO is therefore carried out: in this context a new set of parameters for a pulsed (6 — 8 hours pulse) DEMO is determined working below the density limit, peak temperature of 20 keV, and requiring a modest improvement in the confinement factor(HIPBy2 = 1.1) with respect to the H-mode. Both parameters density and confinement parameter are lower than the DEMO models presently considered. The concept of partially non-inductive pulsed DEMO is introduced since a pulsed DEMO needs heating and current drive tools for plasma stability and burn control. The change of the main parameter design for a DEMO working at high plasma peak temperatures Te ∼ 35 keV is analyzed: in this range the reactivity increases linearly with temperature, and a device with smaller major radius (R = 7.5 m) is compatible with high temperature. Increasing temperature is beneficial for current drive efficiency and heat load on divertor, being the synchrotron radiation one of the relevant components of the plasma emission at high temperatures and current drive efficiency increases with temperature. Technology and engineering problems are examined including efficiency and availability R&D issues for a high temperature DEMO. Fatigue and creep-fatigue effects of pulsed operations on pulsed DEMO components are considered in outline to define the R&D needed for DEMO development. (author)

  18. Classical Dynamics of Free Electromagnetic Laser Pulses

    Goto, S; Tucker, R. W.; Walton, T. J.

    2015-01-01

    We discuss a class of exact finite energy solutions to the vacuum source-free Maxwell field equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged test particles. These solutions are classified in terms of their chiral content based on their influence on particular charge configurations in space. Such solutions offer a computationally efficient parameterization of compact laser pulses used in laser-matter simulations and provide a poten...

  19. Practical issues of retrieving isolated attosecond pulses

    The attosecond streaking technique is used for the characterization of isolated extreme ultraviolet (XUV) attosecond pulses. This type of measurement suffers from low photoelectron counts in the streaked spectrogram, and is thus susceptible to shot noise. For the retrieval of few- or mono-cycle attosecond pulses, high-intensity streaking laser fields are required, which cause the energy spectrum of above-threshold ionized (ATI) electrons to overlap with that of the streaked photoelectrons. It is found by using the principal component generalized projections algorithm that the XUV attosecond pulse can accurately be retrieved for simulated and experimental spectrograms with a peak value of 50 or more photoelectron counts. Also, the minimum streaking intensity is found to be more than 50 times smaller than that required by the classical streaking camera for retrieval of pulses with a spectral bandwidth supporting 90 as transform-limited pulse durations. Furthermore, spatial variation of the streaking laser intensity, collection angle of streaked electrons and time delay jitter between the XUV pulse and streaking field can degrade the quality of the streaked spectrogram. We find that even when the XUV and streaking laser focal spots are comparable in size, the streaking electrons are collected from a 4π solid angle, or the delay fluctuates by more than the attosecond pulse duration, the attosecond pulses can still be accurately retrieved. In order to explain the insusceptibility of the streaked spectrogram to these factors, the linearity of the streaked spectrogram with respect to the streaking field is derived under the saddle point approximation.

  20. Chirped-pulse oscillators: a unified standpoint

    Kalashnikov, V. L.; Apolonski, A.

    2008-01-01

    A completely analytical and unified approach to the theory of chirped-pulse oscillators is presented. The approach developed is based on the approximate integration of the generalized nonlinear complex Ginzburg-Landau equation and demonstrates that a chirped-pulse oscillator is controlled by only two parameters. It makes it easy to trace spread of the real-world characteristics of both solid-state and fiber oscillators operating in the positive dispersion regime.