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Sample records for 39k pulsed endor

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

    Institute of Scientific and Technical Information of China (English)

    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/ENDOR characterization of perturbations of the Cu(A) center ground state by axial methionine ligand mutations.

    Science.gov (United States)

    Slutter, C E; Gromov, I; Epel, B; Pecht, I; Richards, J H; Goldfarb, D

    2001-06-01

    The effect of axial ligand mutation on the Cu(A) site in the recombinant water soluble fragment of subunit II of Thermus thermophilus cytochrome c oxidase ba(3) has been investigated. The weak methionine ligand was replaced by glutamate and glutamine which are stronger ligands. Two constructs, M160T0 and M160T9, that differ in the length of the peptide were prepared. M160T0 is the original soluble fragment construct of cytochrome ba(3) that encodes 135 amino acids of subunit II, omitting the transmembrane helix that anchors the domain in the membrane. In M160T9 nine C-terminal amino acids are missing, including one histidine. The latter has been used to reduce the amount of a secondary T2 copper which is most probably coordinated to a surface histidine in M160T0. The changes in the spin density in the Cu(A) site, as manifested by the hyperfine couplings of the weakly and strongly coupled nitrogens, and of the cysteine beta-protons, were followed using a combination of advanced EPR techniques. X-band ( approximately 9 GHz) electron-spin-echo envelope modulation (ESEEM) and two-dimensional (2D) hyperfine sublevel correlation (HYSCORE) spectroscopy were employed to measure the weakly coupled (14)N nuclei, and X- and W-band (95 GHz) pulsed electron-nuclear double resonance (ENDOR) spectroscopy for probing the strongly coupled (14)N nuclei and the beta-protons. The high field measurements were extremely useful as they allowed us to resolve the T2 and Cu(A) signals in the g( perpendicular) region and gave (1)H ENDOR spectra free of overlapping (14)N signals. The effects of the M160Q and M160E mutations were: (i) increase in A( parallel)((63,65)Cu), (ii) larger hyperfine coupling of the weakly coupled backbone nitrogen of C153, (iii) reduction in the isotropic hyperfine interaction, a(iso), of some of the beta-protons making them more similar, (iv) the a(iso) value of one of the remote nitrogens of the histidine residues is decreased, thus distinguishing the two

  3. Giant Pulses from PSR B1937+21 with widths <= 15 nanoseconds and T_b >= 5 x 10^39 K, the Highest Brightness Temperature Observed in the Universe

    CERN Document Server

    Soglasnov, V A; Bartel, N; Cannon, W; Novikov, A Y; Kondratiev, V I; Altunin, V I

    2004-01-01

    Giant radio pulses of the millisecond pulsar B1937+21 were recorded with the S2 VLBI system at 1.65 GHz with NASA/JPL's 70-m radio telescope at Tidbinbilla, Australia. These pulses have been observed as strong as 65000 Jy with widths = 5 x 10^39 K, the highest observed in the universe. The vast majority of these pulses occur in a 5.8 mcs and 8.2 mcs window at the very trailing edges of the regular main pulse and interpulse profiles, respectively. Giant pulses occur in general with a single spike. Only in one case out of 309 was the structure clearly more complex. The cumulative distribution is fit by a power law with index -1.40 +/- 0.01 with a low-energy but no high-energy cutoff. We estimate that giant pulses occur frequently but are only rarely detected. When corrected for the directivity factor, 25 giant pulses are estimated to be generated in one neutron star revolution alone. The intensities of the giant pulses of the main pulses and interpulses are not correlated with each other nor with the intensitie...

  4. Arsenic speciation in synthetic gypsum (CaSO4·2H2O): A synchrotron XAS, single-crystal EPR, and pulsed ENDOR study

    Science.gov (United States)

    Lin, Jinru; Chen, Ning; Nilges, Mark J.; Pan, Yuanming

    2013-04-01

    Gypsum (CaSO4·2H2O) is a major by-product of mining and milling processes of borate, phosphate and uranium deposits worldwide and, therefore, potentially plays an important role in the stability and bioavailability of heavy metalloids, including As, in tailings and surrounding areas. Gypsum containing 1900 and 185 ppm As, synthesized with Na2HAsO4·7H2O and NaAsO2 in the starting materials, respectively, have been investigated by synchrotron X-ray absorption spectroscopy (XAS), single-crystal electron paramagnetic resonance spectroscopy (EPR), and pulsed electron nuclear double resonance spectroscopy (ENDOR). Quantitative analyses of As K edge XANES and EXAFS spectra show that arsenic occurs in both +3 and +5 oxidation states and the As3+/As5+ value varies from 0.35 to 0.79. Single-crystal EPR spectra of gamma-ray-irradiated gypsum reveal two types of arsenic-associated oxyradicals: [AsO3]2- and an [AsO2]2-. The [AsO3]2- center is characterized by principal 75As hyperfine coupling constants of A1 = 1952.0(2) MHz, A2 = 1492.6(2) MHz and A3 = 1488.7(2) MHz, with the unique A axis along the S-O1 bond direction, and contains complex 1H superhyperfine structures that have been determined by pulsed ENDOR. These results suggest that the [AsO3]2- center formed from electron trapping on the central As5+ ion of a substitutional (AsO4)3- group after removal of an O1 atom. The [AsO2]2- center is characterized by its unique A(75As) axis approximately perpendicular to the O1-S-O2 plane and the A2 axis along the S-O2 bond direction, consistent with electron trapping on the central As3+ ion of a substitutional (AsO3)3- group after removal of an O2 atom. These results confirm lattice-bound As5+ and As3+ in gypsum and point to potential application of this mineral for immobilization and removal of arsenic pollution.

  5. Feshbach resonances in ultracold {sup 39}K

    Energy Technology Data Exchange (ETDEWEB)

    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. The strength of EPR and ENDOR techniques in revealing structure-function relationships in metalloproteins.

    Science.gov (United States)

    Van Doorslaer, Sabine; Vinck, Evi

    2007-09-01

    Recent technological and methodological advances have strongly increased the potential of electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) techniques to characterize the structure and dynamics of metalloproteins. These developments include the introduction of powerful pulsed EPR/ENDOR methodologies and the development of spectrometers operating at very high microwave frequencies and high magnetic fields. This overview focuses on how valuable information about metalloprotein structure-function relations can be obtained using a combination of EPR and ENDOR techniques. After an overview of the historical development and a limited theoretical description of some of the key EPR and ENDOR techniques, their potential will be highlighted using selected examples of applications to iron-, nickel-, cobalt-, and copper-containing proteins. We will end with an outlook of future developments.

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

    OpenAIRE

    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. FID detection of EPR and ENDOR spectra at high microwave frequencies

    Science.gov (United States)

    Blok, H.; Akimoto, I.; Milikisyants, S.; Gast, P.; Groenen, E. J. J.; Schmidt, J.

    2009-11-01

    High-frequency pulsed EPR spectroscopy allows FID detection of EPR spectra owing to the short dead time that can be achieved. This FID detection is particularly attractive for EPR and ENDOR spectroscopy of paramagnetic species that exhibit inhomogeneously broadened EPR lines and short dephasing times. Experiments are reported for the metalloprotein azurin at 275 GHz.

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

    Science.gov (United States)

    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

  10. Production of strongly bound 39K bright solitons

    CERN Document Server

    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.

  11. DFT and ENDOR Study of Bixin Radical Cations and Neutral Radicals on Silica-Alumina.

    Science.gov (United States)

    Tay-Agbozo, Sefadzi S; Krzyaniak, Matthew D; Bowman, Michael K; Street, Shane; Kispert, Lowell D

    2015-06-18

    Bixin, a carotenoid found in annatto (Bixa orellana), is unique among natural carotenoids by being water-soluble. We stabilized free radicals from bixin on the surface of silica-alumina (Si-Al) and characterized them by pulsed electron-nuclear double resonance (ENDOR). DFT calculations of unpaired electron spin distribution for various bixin radicals predict the EPR hyperfine couplings. Least-square fitting of experimental ENDOR spectra by spectra calculated from DFT hyperfine couplings characterized the radicals trapped on Si-Al. DFT predicts that the trans bixin radical cation is more stable than the cis bixin radical cation by 1.26 kcal/mol. This small energy difference is consistent with the 26% trans and 23% cis radical cations in the ENDOR spectrum. The remainder of the ENDOR spectrum is due to several neutral radicals formed by loss of a H(+) ion from the 9, 9', 13, or 13' methyl group, a common occurrence in all water-insoluble carotenoids previously studied. Although carboxyl groups of bixin strongly affect its solubility relative to other natural carotenoids, they do not alter properties of its free radicals based on DFT calculations and EPR measurements which remain similar to typical water-insoluble carotenoids. PMID:25333911

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

    CERN Document Server

    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.

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

    CERN Document Server

    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.

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

    Science.gov (United States)

    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

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

    OpenAIRE

    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, ...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  18. Matrix endor studies of the carbonization of West Canadian coking coals

    Science.gov (United States)

    West, P. R.; Cannon, S. E.

    1981-02-01

    Cretaceous bituminous coals of known rank R¯0 max, vitrinite reflectance) have been examined by ESR (electron spin resonance) and ENDOR (electron nuclear double resonance) techniques. Both highly oxidised (outcrop) and unoxidised mine-run Balmer coal from the Crowsnest field have been subjected to heat treatment (200-900°C), and the matrix proton ENDOR signal studied as a function of applied microwave and rf power. Changes in ENDOR line shape and intensity are described with particular emphasis on the presoftening region of the unoxidised coal. A comparative study of the carbonization of hvb and 1vb coking coal from the Crowsnest is reported.

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

    CERN Document Server

    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.

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

    Science.gov (United States)

    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

  1. Sensitivity Enhancement in Field-Modulated CW ENDOR via RF Bandwidth Broadening

    Science.gov (United States)

    Hoffman, B. M.; Derose, V. J.; Ong, J. L.; Davoust, C. E.

    In low-temperature ENDOR studies it is common to modulate the magnetic field at ν mod ˜ 100 kHz and to observe the ENDOR response as a change in the dispersion-mode rapid-passage EPR signal as decoded at ν mod. The sensitivity of this procedure can be increased by incoherently broadening the bandwidth of the applied RF through mixing of the RF carrier signal with a white-noise source of variable bandwidth. This technique has been explored by monitoring the amplitude and width of ENDOR signals as a function of the RF bandwidth and power, in the case of the 57Fe signals from a metalloprotein and 14N, 1H signals from two Cu(II) compounds. The RF band broadening has produced signal enhancements of over threefold. The results are interpreted in terms of a competition between (i) an increase in the number of spin packets excited within the inhomogeneously broadened ENDOR line and () a reduction in the response per packet. Simple analysis leads to equations for the variation in the ENDOR response with incident RF power and bandwidth that are scaled by a saturation RF power and an effective spin-packet width, respectively.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  3. Electron-mediating Cu(A) centers in proteins: a comparative high field (1)H ENDOR study.

    Science.gov (United States)

    Epel, Boris; Slutter, Claire S; Neese, Frank; Kroneck, Peter M H; Zumft, Walter G; Pecht, Israel; Farver, Ole; Lu, Yi; Goldfarb, Daniella

    2002-07-10

    High field (W-band, 95 GHz) pulsed electron-nuclear double resonance (ENDOR) measurements were carried out on a number of proteins that contain the mixed-valence, binuclear electron-mediating Cu(A) center. These include nitrous oxide reductase (N(2)OR), the recombinant water-soluble fragment of subunit II of Thermus thermophilus cytochrome c oxidase (COX) ba(3) (M160T9), its M160QT0 mutant, where the weak axial methionine ligand has been replaced by a glutamine, and the engineered "purple" azurin (purpAz). The three-dimensional (3-D) structures of these proteins, apart from the mutant, are known. The EPR spectra of all samples showed the presence of a mononuclear Cu(II) impurity with EPR characteristics of a type II copper. At W-band, the g( perpendicular) features of this center and of Cu(A) are well resolved, thus allowing us to obtain a clean Cu(A) ENDOR spectrum. The latter consists of two types of ENDOR signals. The first includes the signals of the four strongly coupled cysteine beta-protons, with isotropic hyperfine couplings, A(iso), in the 7-15 MHz range. The second group consists of weakly coupled protons with a primarily anisotropic character with A(zz) < 3 MHz. Orientation selective ENDOR spectra were collected for N(2)OR, M160QT0, and purpAz, and simulations of the cysteine beta-protons signals provided their isotropic and anisotropic hyperfine interactions. A linear correlation with a negative slope was found between the maximum A(iso) value of the beta-protons and the copper hyperfine interaction. Comparison of the best-fit anisotropic hyperfine parameters with those calculated from dipolar interactions extracted from the available 3-D structures sets limit to the sulfur spin densities. Similarly, the small coupling spectral region was simulated on the basis of the 3-D structures and compared with the experimental spectra. It was found that the width of the powder patterns of the weakly coupled protons recorded at g(perpendicular) is mainly

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    Energy Technology Data Exchange (ETDEWEB)

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

    CERN Document Server

    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.

  7. Multicenter, randomized, tandem evaluation of EndoRings colonoscopy - results of the CLEVER study

    NARCIS (Netherlands)

    Dik, V.K.; Gralnek, I.M.; Segol, O.; Suissa, A.; Belderbos, T.D.; Moons, L.M.; Segev, M.; Domanov, S.; Rex, D.K.; Siersema, P.D.

    2015-01-01

    BACKGROUND AND STUDY AIMS: Adenoma miss rate during colonoscopy has become a widely acknowledged proxy measure for post-colonoscopy colorectal cancer. Among other reasons, this can happen because of inadequate visualization of the proximal aspects of colonic folds and flexures. EndoRings (EndoAid Lt

  8. Multicenter, randomized, tandem evaluation of EndoRings colonoscopy - results of the CLEVER study

    NARCIS (Netherlands)

    Dik, Vincent K; Gralnek, Ian M; Segol, Ori; Suissa, Alain; Belderbos, Tim D G; Moons, Leon M G; Segev, Meytal; Domanov, Sveta; Rex, Douglas K; Siersema, Peter D

    2015-01-01

    Background and study aims: Adenoma miss rate during colonoscopy has become a widely acknowledged proxy measure for post-colonoscopy colorectal cancer. Among other reasons, this can happen because of inadequate visualization of the proximal aspects of colonic folds and flexures. EndoRings (EndoAid Lt

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

    NARCIS (Netherlands)

    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

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

    Science.gov (United States)

    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. 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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    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)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1989-09-01

    The broad goals of this project are to determine by nondestructive means -- magnetic resonance techniques -- aspects of chemical and physical structures of organic parts of native and treated coals. We also hope to use related methods to follow the course of certain coal cleaning processes with microscopic spatial resolution. Specific goals include: the nondestructive determination of atomic and molecular structure of sulfur-containing organic species in coal both in its natural state and at various stages during desulfurization; determination of interatomic distances, numbers, and orientations in individual macerals with differing sulfur content by pulsed EPR microscopy; development of nondestructive high-resolution microscopic images of internal structure in coal, including chemical information on the location and distribution of sulfur-containing compounds; determination of sulfur compound chemical structure from highly localized regions in a whole coal sample; by means of the techniques used to accomplish the above goals, to measure the effects of various coal cleaning methods on the molecular forms and spatial distribution of organic sulfur, and on internal structural characteristics like pore size and maceral density; following by these microscopic methods the rate and extent of solvent intrusion into the pores and matrix of whole coals and separated macerals. The work carried out this year mainly addressed goals 1, 2, 3, and 6. 24 refs., 18 figs.

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

    Energy Technology Data Exchange (ETDEWEB)

    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).

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

    International Nuclear Information System (INIS)

    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)

  17. Thermodynamic Basis of Electron Transfer in Dihydroorotate Dehydrogenase B from Lactococcus lactis:  Analysis by Potentiometry, EPR Spectroscopy, and ENDOR Spectroscopy

    DEFF Research Database (Denmark)

    Mohnsen, Al-Walid A.; Rigby, Stephen E. J.; Jensen, Kaj Frank;

    2004-01-01

    Dihydroorotate dehydrogenase B (DHODB) is a complex iron-sulfur flavoprotein that catalyzes the conversion of dihydroorotate to orotate and the reduction of NAD+. The enzyme is a dimer of heterodimers containing an FMN, an FAD, and a 2Fe-2S center. UV-visible, EPR, and ENDOR spectroscopies have b...

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

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    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)

  20. Thermodynamic basis of electron transfer in dihydroorotate dehydrogenase B from Lactococcus lactis: analysis by potentiometry, EPR spectroscopy, and ENDOR spectroscopy.

    Science.gov (United States)

    Mohsen, Al-Walid A; Rigby, Stephen E J; Jensen, Kaj Frank; Munro, Andrew W; Scrutton, Nigel S

    2004-06-01

    Dihydroorotate dehydrogenase B (DHODB) is a complex iron-sulfur flavoprotein that catalyzes the conversion of dihydroorotate to orotate and the reduction of NAD(+). The enzyme is a dimer of heterodimers containing an FMN, an FAD, and a 2Fe-2S center. UV-visible, EPR, and ENDOR spectroscopies have been used to determine the reduction potentials of the flavins and the 2Fe-2S center and to characterize radicals and their interactions. Reductive titration using dithionite indicates a five-electron capacity for DHODB. The midpoint reduction potential of the 2Fe-2S center (-212 +/- 3 mV) was determined from analysis of absorption data at 540 nm, where absorption contributions from the two flavins are small. The midpoint reduction potentials of the oxidized/semiquinone (E(1)) and semiquinone/hydroquinone (E(2)) couples for the FMN (E(1) = -301 +/- 6 mV; E(2) = -252 +/- 8 mV) and FAD (E(1) = -312 +/- 6 mV; E(2) = -297 +/- 5 mV) were determined from analysis of spectral changes at 630 nm. Corresponding values for the midpoint reduction potentials for FMN (E(1) = -298 +/- 4 mV; E(2) = -259 +/- 5 mV) in the isolated catalytic subunit (subunit D, which lacks the 2Fe-2S center and FAD) are consistent with the values determined for the FMN couples in DHODB. During reductive titration of DHODB, small amounts of the neutral blue semiquinone are observed at approximately 630 nm, consistent with the measured midpoint reduction potentials of the flavins. An ENDOR spectrum of substrate-reduced DHODB identifies hyperfine couplings to proton nuclei similar to those recorded for the blue semiquinone of free flavins in aqueous solution, thus confirming the presence of this species in DHODB. Spectral features observed during EPR spectroscopy of dithionite-reduced DHODB are consistent with the midpoint reduction potentials determined using UV-visible spectroscopy and further identify an unusual EPR signal with very small rhombic anisotropy and g values of 2.02, 1.99, and 1.96. This unusual

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

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

    OpenAIRE

    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...

  4. Pulse on Pulse

    DEFF Research Database (Denmark)

    Schmidt, Ulrik; Carlson, Merete

    2012-01-01

    Pulse on Pulse” 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...

  5. Multi-frequency (S, X, Q and W-band) EPR and ENDOR Study of Vanadium(IV) Incorporation in the Aluminium Metal-Organic Framework MIL-53.

    Science.gov (United States)

    Nevjestić, Irena; Depauw, Hannes; Leus, Karen; Kalendra, Vidmantas; Caretti, Ignacio; Jeschke, Gunnar; Van Doorslaer, Sabine; Callens, Freddy; Van Der Voort, Pascal; Vrielinck, Henk

    2015-10-01

    Doping the well-known metal-organic framework MIL-53(Al) with vanadium(IV) ions leads to significant changes in the breathing behaviour and might have repercussions on the catalytic behaviour as well. To understand the properties of such a doped framework, it is necessary to determine where dopant ions are actually incorporated. Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are applied to reveal the nearest environment of the paramagnetic vanadium(IV) dopant ions. EPR spectra of as-synthesised vanadium-doped MIL-53 are recorded at S-, X-, Q- and W-band microwave frequencies. The EPR spectra suggest that at low dopant concentrations (1.0-2.6 mol %) the vanadium(IV) ions are well dispersed in the matrix. Varying the vanadium dopant concentration within this range or the dopant salt leads to the same dominant EPR component. In the ENDOR spectra, hyperfine (HF) interactions with (1) H, (27) Al and (51) V nuclei are observed. The HF parameters extracted from simulations strongly suggest that the vanadium(IV) ions substitute Al in the framework. PMID:26305910

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

    International Nuclear Information System (INIS)

    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

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

    Directory of Open Access Journals (Sweden)

    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

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

    Science.gov (United States)

    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.

  9. 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

    International Nuclear Information System (INIS)

    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)

  10. Pulse Voltammetry.

    Science.gov (United States)

    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)

  11. Pulse plating

    CERN Document Server

    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...

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

    Science.gov (United States)

    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).

  13. Pulse radiolysis

    International Nuclear Information System (INIS)

    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

  14. PULSE COLUMN

    Science.gov (United States)

    Grimmett, E.S.

    1964-01-01

    This patent covers a continuous countercurrent liquidsolids contactor column having a number of contactor states each comprising a perforated plate, a layer of balls, and a downcomer tube; a liquid-pulsing piston; and a solids discharger formed of a conical section at the bottom of the column, and a tubular extension on the lowest downcomer terminating in the conical section. Between the conical section and the downcomer extension is formed a small annular opening, through which solids fall coming through the perforated plate of the lowest contactor stage. This annular opening is small enough that the pressure drop thereacross is greater than the pressure drop upward through the lowest contactor stage. (AEC)

  15. Excimer Laser Pulse Compress With Pulse Feedback

    Institute of Scientific and Technical Information of China (English)

    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

  16. Inductive Pulse Generation

    OpenAIRE

    Lindblom, Adam

    2006-01-01

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

  17. DIFFERENTIAL PULSE HEIGHT DISCRIMINATOR

    Science.gov (United States)

    Test, L.D.

    1958-11-11

    Pulse-height discriminators are described, specifically a differential pulse-height discriminator which is adapted to respond to pulses of a band of amplitudes, but to reject pulses of amplitudes greater or less than tbe preselected band. In general, the discriminator includes a vacuum tube having a plurality of grids adapted to cut off plate current in the tube upon the application of sufficient negative voltage. One grid is held below cutoff, while a positive pulse proportional to the amplltude of each pulse is applled to this grid. Another grid has a negative pulse proportional to the amplitude of each pulse simultaneously applied to it. With this arrangement the tube will only pass pulses which are of sufficlent amplitude to counter the cutoff bias but not of sufficlent amplitude to cutoff the tube.

  18. Pulse-Width Jitter Measurement for Laser Diode Pulses

    Institute of Scientific and Technical Information of China (English)

    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.

  19. Hybrid chirped pulse amplification system

    Science.gov (United States)

    Barty, Christopher P.; Jovanovic, Igor

    2005-03-29

    A hybrid chirped pulse amplification system wherein a short-pulse oscillator generates an oscillator pulse. The oscillator pulse is stretched to produce a stretched oscillator seed pulse. A pump laser generates a pump laser pulse. The stretched oscillator seed pulse and the pump laser pulse are directed into an optical parametric amplifier producing an optical parametric amplifier output amplified signal pulse and an optical parametric amplifier output unconverted pump pulse. The optical parametric amplifier output amplified signal pulse and the optical parametric amplifier output laser pulse are directed into a laser amplifier producing a laser amplifier output pulse. The laser amplifier output pulse is compressed to produce a recompressed hybrid chirped pulse amplification pulse.

  20. Pulse Pressure in Clinical Practice

    Directory of Open Access Journals (Sweden)

    Jiri Parenica

    2012-02-01

    Full Text Available The review presents basic information about the pulse pressure. The variables related to pulse pressure are briefly explained - arterial stiffness, arterial compliance, pulse wave velocity, pulse pressure amplification and augmentation index. We present some recent trials and observational studies that show the importance of pulse pressure in clinical practice. Briefly the possibilities of influencing the pulse pressure are discussed.

  1. Pulsed laser machining apparatus

    International Nuclear Information System (INIS)

    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

  2. Nonlinear pulse compression

    OpenAIRE

    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...

  3. Opportunities in pulse combustion

    Science.gov (United States)

    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.

  4. Pulsed Plasma Electron Sources

    Science.gov (United States)

    Krasik, Yakov

    2008-11-01

    Pulsed (˜10-7 s) electron beams with high current density (>10^2 A/cm^2) are generated in diodes with electric field of E > 10^6 V/cm. The source of electrons in these diodes is explosive emission plasma, which limits pulse duration; in the case E Hadas and Ya. E. Krasik, Europhysics Lett. 82, 55001 (2008).

  5. DogPulse

    DEFF Research Database (Denmark)

    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 c...

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

    OpenAIRE

    Lali-Dastjerdi, Zohreh; Da Ros, Francesco; Rottwitt, Karsten; Galili, Michael; Peucheret, Christophe

    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.

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

    DEFF Research Database (Denmark)

    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....

  8. Efficient Pulsed Quadrupole

    CERN Document Server

    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. Pulse joining cartridges

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. Intense pulsed neutron sources

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Pulse Coil Tester

    Science.gov (United States)

    Simon, Richard A.

    1988-01-01

    Set of relays tested easily and repeatedly. Pulse coil tester causes coil under test to generate transient voltage; waveform indicates condition of coil. Tester accommodates assembly of up to four coils at a time.

  12. A directive pulse antenna

    OpenAIRE

    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. Ultrashort pulse induced nanogratings

    Directory of Open Access Journals (Sweden)

    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.

  14. Magnetic Pulse Welding Technology

    OpenAIRE

    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...

  15. Pulsed spallation Neutron Sources

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. High voltage pulse generator

    Science.gov (United States)

    Fasching, George E.

    1977-03-08

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

  17. Herophilus on pulse

    Directory of Open Access Journals (Sweden)

    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.

  18. Pulsed Artificial Electrojet Generation

    Science.gov (United States)

    Papadopoulos, K.

    2008-12-01

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

  19. Pulse Doppler radar

    CERN Document Server

    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

  20. Millimicrosecond pulse techniques

    CERN Document Server

    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

  1. SNMR pulse sequence phase cycling

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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%.

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

    Science.gov (United States)

    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

  4. Lectures on pulsed NMR

    Energy Technology Data Exchange (ETDEWEB)

    Pines, A.

    1986-09-01

    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.

  5. Downhole pulse tube refrigerators

    Energy Technology Data Exchange (ETDEWEB)

    Swift, G.; Gardner, D. [Los Alamos National Lab., NM (United States). Condensed Matter and Thermal Physics Group

    1997-12-01

    This report summarizes a preliminary design study to explore the plausibility of using pulse tube refrigeration to cool instruments in a hot down-hole environment. The original motivation was to maintain Dave Reagor`s high-temperature superconducting electronics at 75 K, but the study has evolved to include three target design criteria: cooling at 30 C in a 300 C environment, cooling at 75 K in a 50 C environment, cooling at both 75 K and 30 C in a 250 C environment. These specific temperatures were chosen arbitrarily, as representative of what is possible. The primary goals are low cost, reliability, and small package diameter. Pulse-tube refrigeration is a rapidly growing sub-field of cryogenic refrigeration. The pulse tube refrigerator has recently become the simplest, cheapest, most rugged and reliable low-power cryocooler. The authors expect this technology will be applicable downhole because of the ratio of hot to cold temperatures (in absolute units, such as Kelvin) of interest in deep drilling is comparable to the ratios routinely achieved with cryogenic pulse-tube refrigerators.

  6. Analog pulse processor

    Science.gov (United States)

    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.

  7. Hybrid Chirped Pulse Amplification

    Energy Technology Data Exchange (ETDEWEB)

    Jovanovic, I; Barty, C P J

    2002-05-07

    We present a novel chirped pulse amplification method which combines optical parametric amplification and laser amplification. We have demonstrated this hybrid CPA concept with a combination of beta-barium borate and Ti:sapphire. High-efficiency, multi-terawatt compatible amplification is achieved without gain narrowing and without electro-optic modulators using a simple commercial pump laser.

  8. Recent advances in pulse oximetry

    OpenAIRE

    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...

  9. Sequentially pulsed traveling wave accelerator

    Science.gov (United States)

    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.

  10. Bacterial inactivation using pulsed light

    OpenAIRE

    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...

  11. Pulsed power for EMP simulators

    International Nuclear Information System (INIS)

    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

  12. Design of a pulse stacker

    International Nuclear Information System (INIS)

    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.)

  13. Short pulse neutron generator

    Energy Technology Data Exchange (ETDEWEB)

    Elizondo-Decanini, Juan M.

    2016-08-02

    Short pulse neutron generators are described herein. In a general embodiment, the short pulse neutron generator includes a Blumlein structure. The Blumlein structure includes a first conductive plate, a second conductive plate, a third conductive plate, at least one of an inductor or a resistor, a switch, and a dielectric material. The first conductive plate is positioned relative to the second conductive plate such that a gap separates these plates. A vacuum chamber is positioned in the gap, and an ion source is positioned to emit ions in the vacuum chamber. The third conductive plate is electrically grounded, and the switch is operable to electrically connect and disconnect the second conductive plate and the third conductive plate. The at least one of the resistor or the inductor is coupled to the first conductive plate and the second conductive plate.

  14. Magnetic Pulse Welding Technology

    Directory of Open Access Journals (Sweden)

    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.

  15. Pulsed fusion reactors

    International Nuclear Information System (INIS)

    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

  16. Training Ultrafast Laser Pulses

    Science.gov (United States)

    Averin, Ruslan; Wells, N.; Todt, M.; Smolnisky, N.; Jastram, N.; Jochim, B.; Gregerson, N.; Wells, E.; Sayler, A.; McKenna, J.; Carnes, K.; Ben-Itzhak, I.; Kling, M. F.

    2009-11-01

    Closed loop control of molecular processes utilizing shaped ultrafast laser pulses has been around for a number of years, yet this type of control has primarily utilized Time of Flight ion yield data for feedback. We present experiments using Velocity Map Imaging (VMI) as the feedback source for the closed loop control. Using VMI allows for pulse optimization not only with respect to the disassociation species but also angular information of the final state. We demonstrate the feasibility of incorporating this kind of feedback into the control loop. Using this technique, we controlled the dissociation branching ratio of CO^+ into C^+ +O or C ^+O^+ and used the VMI information to recover additional information about the control mechanism.

  17. Computationally intelligent pulsed photoacoustics

    International Nuclear Information System (INIS)

    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)

  18. Pulsed electron beam precharger

    Energy Technology Data Exchange (ETDEWEB)

    Finney, W.C. (ed.); Shelton, W.N.

    1989-01-01

    This is the fifth in a series of contracts and grants exploring the advanced particulate pollution control technology of electron beam precipitation. The chief goal of the current contract is to develop a laboratory scale electron beam precharger using a pulsed electric field to the proof-of-concept stage. Contract tasks leading to the achievement of this goal are generally divided up into two categories: tasks required to bring the Electron Beam Precipitator (EBP) test system up to an operational level for the contract work, and tasks concerning the actual experimental and analytical phase of the study. Not unexpectedly, the early portion of the contract duration will be devoted to the commissioning of the EBP and its many subsystems, while the latter portion will devote itself to testing the new pulsed electron beam precharger.

  19. Micro pulse laser radar

    Science.gov (United States)

    Spinhirne, James D. (Inventor)

    1993-01-01

    An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering is disclosed. The transmitter of the micro pulse lidar is a diode pumped micro-J pulse energy, high repetition rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver employs a photon counting solid state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited to optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that micropulse lider systems are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere. The intended applications are scientific studies and environmental monitoring which require full time, unattended measurements of the cloud and aerosol height structure.

  20. Measurement of pulse lengthening with pulse energy increase in picosecond Nd:YAG laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Cutolo, A.; Zeni, L.; Berardi, V.; Bruzzese, R.; Solimeno, S.; Spinelli, N.

    1989-03-15

    Taking advantage of a new technique, we have monitored the relative variations of time duration and mode size as a function of the pulse energy for 30-ps-long Nd:YAG laser pulses. In particular, by carrying out a statistical analysis, we have observed that the pulse time duration is an increasing function of the pulse energy, according to the theoretical modeling of passively mode-locked lasers. The measurements can be easily extended to the femtosecond regime.

  1. Pulsed laser microtomograph

    Science.gov (United States)

    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.

  2. Twitter's visual pulse

    OpenAIRE

    Hare, Jonathon; Samangooei, Sina; Dupplaw, David; Lewis, Paul H.

    2013-01-01

    Millions of images are tweeted every day, yet very little research has looked at the non-textual aspect of social media communication. In this work we have developed a system to analyse streams of image data. In particular we explore trends in similar, related, evolving or even duplicated visual artefacts in the mass of tweeted image data — in short, we explore the visual pulse of Twitter.

  3. A volcano's pulse

    OpenAIRE

    Loughlin, Sue

    2010-01-01

    Before the 1995 Soufrière Hills eruption began, there had been seismic crises approximately every 30 years since the late 1890s; each crisis lasted months to years and involved thousands of small earthquakes. In 1935, some earthquakes were large enough to cause damage to buildings in the capital Plymouth and there was real concern that an eruption was imminent. These seismic crises were later interpreted as pulses of magma trying, but failing, to reach the surface. A final seis...

  4. Compact pulsed accelerator

    International Nuclear Information System (INIS)

    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

  5. Pulse Portraiture: Pulsar timing

    Science.gov (United States)

    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).

  6. STUCTURE OF PULSED BED

    Directory of Open Access Journals (Sweden)

    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.

  7. Pulsed Superconductivity Acceleration

    CERN Document Server

    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...

  8. Pulse radiolysis of gases

    International Nuclear Information System (INIS)

    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)

  9. Petawatt pulsed-power accelerator

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. Band-selective radiofrequency pulses

    Science.gov (United States)

    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.

  11. Quarter-wave pulse tube

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    Burkhart, Scott C.

    2002-01-01

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

  13. Coiled transmission line pulse generators

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, Kenneth Fox (Columbia, MO)

    2010-11-09

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

  14. Versatile pulse programmer for pulsed nuclear magnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    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

  15. Green Light Pulse Oximeter

    Energy Technology Data Exchange (ETDEWEB)

    Scharf, John Edward (Oldsmar, FL)

    1998-11-03

    A reflectance pulse oximeter that determines oxygen saturation of hemoglobin using two sources of electromagnetic radiation in the green optical region, which provides the maximum reflectance pulsation spectrum. The use of green light allows placement of an oximetry probe at central body sites (e.g., wrist, thigh, abdomen, forehead, scalp, and back). Preferably, the two green light sources alternately emit light at 560 nm and 577 nm, respectively, which gives the biggest difference in hemoglobin extinction coefficients between deoxyhemoglobin, RHb, and oxyhemoglobin, HbO.sub.2.

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

    Science.gov (United States)

    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

  17. Pulse front tilt measurement of femtosecond laser pulses

    Science.gov (United States)

    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.

  18. COMPUTER BASED HEART PULSES MEASUREMENT

    Directory of Open Access Journals (Sweden)

    Ali N. Hamoodi

    2013-05-01

    Full Text Available In this work the measurement and displays of blood oxygen saturation and pulse rate are investigated practically using computer.The analysis involves the variation in blood oxygen saturation ratio and pulse rate. The results obtained are compared with kontron pulse oximeter 7840 device. The value obtained for the same person pulse rate is approximately equal to that obtained by the konton pulse oximeter 7840 device. The sensor used in this work is the finger clip.The advantages of using computer over kontron pulse oximeter 7840 device is that the data of the patient can be saved in the computer for many years and also it can be display at any time so that the doctor get file contains all data for each patient. 

  19. Heat driven pulse pump

    Science.gov (United States)

    Benner, Steve M (Inventor); Martins, Mario S. (Inventor)

    2000-01-01

    A heat driven pulse pump includes a chamber having an inlet port, an outlet port, two check valves, a wick, and a heater. The chamber may include a plurality of grooves inside wall of the chamber. When heated within the chamber, a liquid to be pumped vaporizes and creates pressure head that expels the liquid through the outlet port. As liquid separating means, the wick, disposed within the chamber, is to allow, when saturated with the liquid, the passage of only liquid being forced by the pressure head in the chamber, preventing the vapor from exiting from the chamber through the outlet port. A plurality of grooves along the inside surface wall of the chamber can sustain the liquid, which is amount enough to produce vapor for the pressure head in the chamber. With only two simple moving parts, two check valves, the heat driven pulse pump can effectively function over the long lifetimes without maintenance or replacement. For continuous flow of the liquid to be pumped a plurality of pumps may be connected in parallel.

  20. Compensated pulsed alternator

    International Nuclear Information System (INIS)

    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

  1. Gravitational Pulse Astronomy

    CERN Document Server

    Gould, Andrew

    2010-01-01

    Thompson has recently argued that the Kozai mechanism is primarily responsible for driving white-dwarf binary mergers and so generating type Ia supernovae (SNe). If this is the case, the gravitational wave signal from these systems will be characterized by isolated repeating pulses that are well approximated by parabolic encounters. I show that standard Fourier-based searches would do a very poor job of digging these sources out of the noise, and propose a new type matched filter search, which can improve sensitivity by up to a factor ~30 relative to Fourier. If these eccentric binaries account for even a modest fraction of the observed SN rate, then there should be of order 1 pulse every 20 seconds coming from within 1 kpc, and there should be of order a thousand detectable sources in this same volume. I outline methods of identifying these sources both to remove this very pernicious background to other signals, and to find candidate SN Ia progenitors, and I sketch practical methods to find optical counterpa...

  2. Assembly delay line pulse generators

    CERN Multimedia

    1971-01-01

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

  3. Programming Pulse Driven Quantum Computers

    OpenAIRE

    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.

  4. A microsecond pulse radiolysis apparatus

    International Nuclear Information System (INIS)

    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

  5. Klystron pulse mudulator for linac

    International Nuclear Information System (INIS)

    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.)

  6. Pulse oximetry in severe anaemia

    DEFF Research Database (Denmark)

    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....

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

    Institute of Scientific and Technical Information of China (English)

    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.

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

    International Nuclear Information System (INIS)

    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.)

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

    Energy Technology Data Exchange (ETDEWEB)

    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.)

  10. Capacitor discharge pulse analysis.

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Nonlinear Femtosecond Pulse Reshaping in Waveguide Arrays

    OpenAIRE

    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.

  12. NMR in pulsed magnetic field

    KAUST Repository

    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.

  13. Pulse oximetry for perioperative monitoring

    DEFF Research Database (Denmark)

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

    2014-01-01

    of perioperative monitoring with pulse oximetry to clearly identify adverse outcomes that might be prevented or improved by its use.The following hypotheses were tested.1. Use of pulse oximetry is associated with improvement in the detection and treatment of hypoxaemia.2. Early detection and treatment...... of perioperative monitoring with pulse oximetry. A single study in general surgery showed that postoperative complications occurred in 10% of participants in the oximetry group and in 9.4% of those in the control group. No statistically significant differences in cardiovascular, respiratory, neurological...... after cardiothoracic surgery; however, routine continuous monitoring did not reduce transfer to an ICU and did not decrease overall mortality. AUTHORS' CONCLUSIONS: These studies confirmed that pulse oximetry can detect hypoxaemia and related events. However, we found no evidence that pulse oximetry...

  14. Pre-earthquake Magnetic Pulses

    CERN Document Server

    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.

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

    Directory of Open Access Journals (Sweden)

    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

    Science.gov (United States)

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  18. Pulse source requirements for OTDM systems

    DEFF Research Database (Denmark)

    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....

  19. Bomb pulse biology

    Energy Technology Data Exchange (ETDEWEB)

    Falso, Miranda J. Sarachine [Center for Accelerator Mass Spectrometry, Mail Stop L-397, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States); Buchholz, Bruce A., E-mail: buchholz2@llnl.gov [Center for Accelerator Mass Spectrometry, Mail Stop L-397, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States)

    2013-01-15

    The past decade has seen an explosion in use of the {sup 14}C bomb pulse to do fundamental cell biology. Studies in the 1960s used decay counting to measure tissue turnover when the atmospheric {sup 14}C/C concentration was changing rapidly. Today bulk tissue measurements are of marginal interest since most of the carbon in the tissue resides in proteins, lipids and carbohydrates that turn over rapidly. Specific cell types with specialized functions are the focus of cell turnover investigations. Tissue samples need to be fresh or frozen. Fixed or preserved samples contain petroleum-derived carbon that has not been successfully removed. Cell or nuclear surface markers are used to sort specific cell types, typically by fluorescence-activated cell sorting (FACS). Specific biomolecules need to be isolated with high purity and accelerator mass spectrometry (AMS) measurements must accommodate samples that generally contain less than 40 {mu}g of carbon. Furthermore, all separations must not add carbon to the sample. Independent means such as UV absorbance must be used to confirm molecule purity. Approaches for separating specific proteins and DNA and combating contamination of undesired molecules are described.

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

    International Nuclear Information System (INIS)

    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. Magnetic Alignment of Pulsed Solenoids Using the Pulsed Wire Method

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Giant pulses in Millisecond Pulsars

    CERN Document Server

    Joshi, B C; Lyne, A G; McLaughlin, M; Stairs, I H

    2003-01-01

    Giant pulses (GPs), occasional individual pulses with an intensity 100 times the average intensity, have been detected in four pulsars todate. Their origin is not well understood, but studies suggest a connection between the strength of magnetic field at the light cylinder B_lc and the existence of GPs. Here, we report on detection of significant Large Amplitude Pulses (LAPs) in two more pulsars with high values of B_lc, PSRs J0218+4232 and B1957+20, observed using Giant Meterwave Radio Telescope (GMRT).

  3. Pulsed ultrasonic stir welding method

    Science.gov (United States)

    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.

  4. Hyper dispersion pulse compressor for chirped pulse amplification systems

    Energy Technology Data Exchange (ETDEWEB)

    Barty, Christopher P. J. (Hayward, CA)

    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.

  5. Pulse-to-pulse Diagnostics at High Reprate

    Science.gov (United States)

    Green, Bertram; Kovalev, Sergey; Golz, Torsten; Stojanovich, Nikola; Fisher, Alan; Kampfrath, Tobias; Gensch, Michael

    2016-03-01

    Femtosecond level diagnostic and control of sub-picosecond electron bunches is an important topic in modern accelerator research. At the same time new linear electron accelerators based on quasi-CW SRF technology will be the drivers of many future 4th Generation lightsources such as X-ray free electron lasers. A high duty cycle, high stability and online pulse to pulse diagnostic at these new accelerators are crucial ingredients to the success of these large scale facilities. A novel THz based online monitor concept is presented that has the potential to give access to pulse to pulse information on bunch form, arrival time and energy at high repetition rate and down to sub pC charges. We furthermore show experimentally that pulse to pulse arrival time measurements can be used to perform pump-probe experiments with a temporal resolution in the few-fs regime and an exceptional dynamic range. Our scheme has been tested at the superradiant test facility TELBE, but can be readily transferred to other SRF accelerator driven photon sources, such as X-FELs.

  6. Pulsed Corona for Sustainable Technology

    International Nuclear Information System (INIS)

    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)

  7. Rapidly pulsed helium droplet source

    Energy Technology Data Exchange (ETDEWEB)

    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.

  8. Next generation Chirped Pulse Amplification

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

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

  9. Artistic Representation with Pulsed Holography

    Science.gov (United States)

    Ishii, S.

    2013-02-01

    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.

    Directory of Open Access Journals (Sweden)

    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

    CERN Document Server

    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

    Science.gov (United States)

    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. Artistic Representation with Pulsed Holography

    International Nuclear Information System (INIS)

    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.

  14. Video Processor for Transponder Pulses

    Science.gov (United States)

    Byrne, F.

    1986-01-01

    Circuit detects interrogation signals from air-traffic-control station and determines whether transponder of airplane should respond. Circuit examines relative magnitudes of first two pulses in three-pulse sequence of interrogation signal. On basis of relative magnitudes, circuit decides whether main lobe of interrogating radar beam is received (response should be generated) or only side lobe received (and interrogation ignored). Circuit simple and inexpensive.

  15. Pulsed power molten salt battery

    Science.gov (United States)

    Argade, Shyam D.

    1992-02-01

    It was concluded that carbon cathodes with chlorine work well. Lithium alloy chlorine at 450 C, 1 atm given high power capability, high energy density, DC + pulsing yields 600 pulses, no initial peak, and can go to red heat without burn-up. Electrochemical performance at the cell and cell stack level out under demanding test regime. Engineering and full prototype development for advancing this technology is warranted.

  16. The Toulouse pulsed magnet facility

    International Nuclear Information System (INIS)

    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

  17. Millijoule pulse energy picosecond fiber chirped-pulse amplification system

    Institute of Scientific and Technical Information of China (English)

    Zhi Yang; Xiaohong Hu; Yishan Wang; Wei Zhang; Wei Zhao

    2011-01-01

    @@ The efficient generation of a 1.17-mJ laser pul8e with 360 ps duration using an ytterbium (Yb)-doped fiber amplifier chain seeded by a homemade mode-locked fiber laser is demonstrated experimentally.A specially designed figure-of-eight fiber laser acts as the seed source of a chirped-pulse amplification (CPA) system and generates mode-locked pulse8 with hundreds of picosecond widths.Two kinds of large-mode-area (LMA) double-clad Yb-doped fibers are employed to construct the pre-amplifier and main amplifier, All of the adopted instruments help avoid severe nonlinearity in fibers to raise sub-nanosecond pulse energy with acceptable signal-to-noise ratio (SNR).The output spectrum of this fiber-based CPA system shows that amplified spontaneous emission (ASE) is suppressed to better than 30 dB, and the onset of stimulated Raman scattering is excluded.%The efficient generation of a 1.17-mJ laser pulse with 360 ps duration using an ytterbium (Yb)-doped fiber amplifier chain seeded by a homemade mode-locked fiber laser is demonstrated experimentally. A specially designed figure-of-eight fiber laser acts as the seed source of a chirped-pulse amplification (CPA) system and generates mode-locked pulses with hundreds of picosecond widths. Two kinds of large-mode-area (LMA) double-clad Yb-doped fibers are employed to construct the pre-amplifier and main amplifier. All of the adopted instruments help avoid severe nonlinearity in fibers to raise sub-nanosecond pulse energy with acceptable signal-to-noise ratio (SNR). The output spectrum of this fiber-based CPA system shows that amplified spontaneous emission (ASE) is suppressed to better than 30 dB, and the onset of stimulated Raman scattering is excluded.

  18. A nanosecond pulsed accelerator facility

    International Nuclear Information System (INIS)

    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

  19. Pulse compression and prepulse suppression apparatus

    Science.gov (United States)

    Dane, C.B.; Hackel, L.A.; George, E.V.; Miller, J.L.; Krupke, W.F.

    1993-11-09

    A pulse compression and prepulse suppression apparatus (10) for time compressing the output of a laser (14). A pump pulse (46) is separated from a seed pulse (48) by a first polarized beam splitter (20) according to the orientation of a half wave plate (18). The seed pulse (48) is directed into an SBS oscillator (44) by two plane mirrors (22, 26) and a corner mirror (24), the corner mirror (24) being movable to adjust timing. The pump pulse (46) is directed into an SBS amplifier 34 wherein SBS occurs. The seed pulse (48), having been propagated from the SBS oscillator (44), is then directed through the SBS amplifier (34) wherein it sweeps the energy of the pump pulse (46) out of the SBS amplifier (34) and is simultaneously compressed, and the time compressed pump pulse (46) is emitted as a pulse output (52). A second polarized beam splitter (38) directs any undepleted pump pulse 58 away from the SBS oscillator (44).

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

    Science.gov (United States)

    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.

  1. The coherent artifact in modern pulse measurements

    CERN Document Server

    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.

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

    Science.gov (United States)

    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.

  3. Wide Range SET Pulse Measurement

    Science.gov (United States)

    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. The pulsing CPSD method for subcritical assemblies with pulsed sources

    CERN Document Server

    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.

  5. Pre-earthquake magnetic pulses

    Directory of Open Access Journals (Sweden)

    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.

  6. Pulsed liquid microjet for microsurgery

    Science.gov (United States)

    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.

  7. Radial flow pulse jet mixer

    Science.gov (United States)

    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.

  8. Pulsed neutron sources at Dubna

    International Nuclear Information System (INIS)

    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)

  9. Pulsed discharge production Ar* metastables

    Science.gov (United States)

    Han, Jiande; Heaven, Michael C.; Emmons, Daniel; Perram, Glen P.; Weeks, David E.; Bailey, William F.

    2016-03-01

    The production of relatively high densities of Ar* metastables (>1012 cm-3) in Ar/He mixtures, at total pressures close to 1 atm, is essential for the efficient operation of an optically pumped Ar* laser. We have used emission spectroscopy and diode laser absorption spectroscopy measurements to observe the production and decay of Ar* in a parallel plate pulsed discharge. With discharge pulses of 1 μs duration we find that metastable production is dominated by processes occurring within the first 100 ns of the gas break-down. Application of multiple, closely spaced discharge pulses yields insights concerning conditions that favor metastable production. This information has been combined with time-resolved measurements of voltage and current. The experimental results and preliminary modeling of the discharge kinetics are presented.

  10. Zeptosecond $\\gamma$-ray pulses

    CERN Document Server

    Klaiber, Michael; Keitel, Christoph H

    2007-01-01

    High-order harmonic generation (HHG) in the relativistic regime is employed to obtain zeptosecond pulses of $\\gamma$-rays. The harmonics are generated from atomic systems in counterpropagating strong attosecond laser pulse trains of linear polarization. In this setup recollisions of the ionized electrons can be achieved in the highly relativistic regime via a reversal of the commonly deteriorating drift and without instability of the electron dynamics such as in a standing laser wave. As a result, coherent attosecond $\\gamma$-rays in the 10 MeV energy range as well as coherent zeptosecond $\\gamma$-ray pulses of MeV photon energy for time-resolved nuclear spectroscopy become feasible.

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

    OpenAIRE

    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...

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

    Science.gov (United States)

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

    2011-06-20

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

  13. Pulse compressor with aberration correction

    Energy Technology Data Exchange (ETDEWEB)

    Mankos, Marian [Electron Optica, Inc., Palo Alto, CA (United States)

    2015-11-30

    In this SBIR project, Electron Optica, Inc. (EOI) is developing an electron mirror-based pulse compressor attachment to new and retrofitted dynamic transmission electron microscopes (DTEMs) and ultrafast electron diffraction (UED) cameras for improving the temporal resolution of these instruments from the characteristic range of a few picoseconds to a few nanoseconds and beyond, into the sub-100 femtosecond range. The improvement will enable electron microscopes and diffraction cameras to better resolve the dynamics of reactions in the areas of solid state physics, chemistry, and biology. EOI’s pulse compressor technology utilizes the combination of electron mirror optics and a magnetic beam separator to compress the electron pulse. The design exploits the symmetry inherent in reversing the electron trajectory in the mirror in order to compress the temporally broadened beam. This system also simultaneously corrects the chromatic and spherical aberration of the objective lens for improved spatial resolution. This correction will be found valuable as the source size is reduced with laser-triggered point source emitters. With such emitters, it might be possible to significantly reduce the illuminated area and carry out ultrafast diffraction experiments from small regions of the sample, e.g. from individual grains or nanoparticles. During phase I, EOI drafted a set of candidate pulse compressor architectures and evaluated the trade-offs between temporal resolution and electron bunch size to achieve the optimum design for two particular applications with market potential: increasing the temporal and spatial resolution of UEDs, and increasing the temporal and spatial resolution of DTEMs. Specialized software packages that have been developed by MEBS, Ltd. were used to calculate the electron optical properties of the key pulse compressor components: namely, the magnetic prism, the electron mirror, and the electron lenses. In the final step, these results were folded

  14. Pulsed neutron porosity logging system

    International Nuclear Information System (INIS)

    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

  15. High-speed pulse techniques

    CERN Document Server

    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

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

    Science.gov (United States)

    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.

  17. Neuromuscular disruption with ultrashort electrical pulses

    Science.gov (United States)

    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.

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

    DEFF Research Database (Denmark)

    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....

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

    OpenAIRE

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

    2005-01-01

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

  20. Wave equations for pulse propagation

    Science.gov (United States)

    Shore, B. W.

    1987-06-01

    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.

  1. Pulsed neutron generator for logging

    International Nuclear Information System (INIS)

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

  2. Ptychographic reconstruction of attosecond pulses

    CERN Document Server

    Lucchini, M; Ludwig, A; Gallmann, L; Keller, U; Feurer, T

    2015-01-01

    We demonstrate a new attosecond pulse reconstruction modality which uses an algorithm that is derived from ptychography. In contrast to other methods, energy and delay sampling are not correlated, and as a result, the number of electron spectra to record is considerably smaller. Together with the robust algorithm, this leads to a more precise and fast convergence of the reconstruction.

  3. Ultrashort-pulse laser machining

    Energy Technology Data Exchange (ETDEWEB)

    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.

  4. Ultrashort-pulse lasers machining

    Energy Technology Data Exchange (ETDEWEB)

    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.

  5. Nonparametric estimation of ultrasound pulses

    DEFF Research Database (Denmark)

    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...

  6. Cryosurgery with pulsed electric fields.

    Directory of Open Access Journals (Sweden)

    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

  7. Pulse frequency classification based on BP neural network

    Institute of Scientific and Technical Information of China (English)

    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.

  8. Treatment Pulse Application for Magnetic Stimulation

    Directory of Open Access Journals (Sweden)

    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.

  9. Digital Communication Using Chaotic Pulse Generators

    CERN Document Server

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

    1999-01-01

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

  10. Exact Solutions to Short Pulse Equation

    Institute of Scientific and Technical Information of China (English)

    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.

  11. Nature of giant pulses in radio pulsars

    CERN Document Server

    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.

  12. Dispersion compensation in chirped pulse amplification systems

    Science.gov (United States)

    Bayramian, Andrew James; Molander, William A.

    2014-07-15

    A chirped pulse amplification system includes a laser source providing an input laser pulse along an optical path. The input laser pulse is characterized by a first temporal duration. The system also includes a multi-pass pulse stretcher disposed along the optical path. The multi-pass pulse stretcher includes a first set of mirrors operable to receive input light in a first plane and output light in a second plane parallel to the first plane and a first diffraction grating. The pulse stretcher also includes a second set of mirrors operable to receive light diffracted from the first diffraction grating and a second diffraction grating. The pulse stretcher further includes a reflective element operable to reflect light diffracted from the second diffraction grating. The system further includes an amplifier, a pulse compressor, and a passive dispersion compensator disposed along the optical path.

  13. Developing classification indices for Chinese pulse diagnosis

    CERN Document Server

    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...

  14. Linear transformer driver for pulse generation

    Science.gov (United States)

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

    2015-04-07

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

  15. Methods for High Power EM Pulse Measurement

    OpenAIRE

    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...

  16. Dynamic pulsing of a MOPA fiber laser

    Science.gov (United States)

    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.

  17. High Power Picosecond Laser Pulse Recirculation

    Energy Technology Data Exchange (ETDEWEB)

    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.

  18. Complementarity of long pulse and short pulse spallation sources

    International Nuclear Information System (INIS)

    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

  19. REFLECTANCE PULSE OXIMETRY IN FETAL LAMBS

    NARCIS (Netherlands)

    DASSEL, AC; GRAAFF, R; AARNOUDSE, JG; ELSTRODT, JM; HEIDA, P; KOELINK, MH; DEMUL, FF; GREVE, J

    1992-01-01

    Transmission pulse oximetry is used for monitoring in many clinical settings. However, for fetal monitoring during labor and in situations with poor peripheral perfusion, transmission pulse oximetry cannot be used. Therefore, we developed a reflectance pulse oximeter, which uses the relative intensi

  20. <3> OMEGA pulse-forming network

    CERN Multimedia

    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.

  1. Double pulse Thomson scattering system at RTP

    NARCIS (Netherlands)

    Beurskens, M. N. A.; Barth, C. J.; Chu, C.C.; Donne, A. J. H.; Herranz, J. A.; Cardozo, N. J. L.; van der Meiden, H. J.; Pijper, F.J.

    1997-01-01

    In this article a double pulse multiposition Thomson scattering diagnostic, under construction at RTP, is discussed. Light from a double pulsed ruby laser (pulse separation: 10-800 mu s, max. 2x12.5 J) is scattered by the free electrons of the tokamak plasma and relayed to a Littrow polychromator fo

  2. Perceptions of European stakeholders of pulse fishing

    NARCIS (Netherlands)

    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

  3. A transformer of closely spaced pulsed waveforms

    Science.gov (United States)

    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.

  4. A Method for Distinguishing Attosecond Single Pulse from Attosecond Pulse Train

    Institute of Scientific and Technical Information of China (English)

    HUO Yi-Ping; ZENG Zhi-Nan; LI Ru-Xin; XU Zhi-Zhan

    2004-01-01

    @@ The driving laser field assisted attosecond soft-extreme-ultraviolet (XUV) photo-ionization was used successfully to measure the duration of the attosecond pulse based on the cross-correlation method. However, this method in principle cannot distinguish a single attosecond pulse from the attosecond pulse train. We propose a technique for directly distinguishing attosecond single pulse from attosecond pulse train based on the photo-ionization of atoms by attosecond XUV pulse in the presence of a two-colour strong laser pulse.

  5. CW seeded optical parametric amplifier providing wavelength and pulse duration tunable nearly transform limited pulses.

    Science.gov (United States)

    Hädrich, S; Gottschall, T; Rothhardt, J; Limpert, J; Tünnermann, A

    2010-02-01

    An optical parametric amplifier that delivers nearly transform limited pulses is presented. The center wavelength of these pulses can be tuned between 993 nm and 1070 nm and, at the same time, the pulse duration is varied between 206 fs and 650 fs. At the shortest pulse duration the pulse energy was increased up to 7.2 microJ at 50 kHz repetition rate. Variation of the wavelength is achieved by applying a tunable cw seed while the pulse duration can be varied via altering the pump pulse duration. This scheme offers superior flexibility and scaling possibilities.

  6. Pulse Propagation on close conductors

    CERN Document Server

    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.

  7. Pulsed metallic-plasma generators.

    Science.gov (United States)

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

    1972-01-01

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

  8. Powerful microsecond voltage pulse generator

    International Nuclear Information System (INIS)

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

  9. Optimal filter bandwidth for pulse oximetry

    Science.gov (United States)

    Stuban, Norbert; Niwayama, Masatsugu

    2012-10-01

    Pulse oximeters contain one or more signal filtering stages between the photodiode and microcontroller. These filters are responsible for removing the noise while retaining the useful frequency components of the signal, thus improving the signal-to-noise ratio. The corner frequencies of these filters affect not only the noise level, but also the shape of the pulse signal. Narrow filter bandwidth effectively suppresses the noise; however, at the same time, it distorts the useful signal components by decreasing the harmonic content. In this paper, we investigated the influence of the filter bandwidth on the accuracy of pulse oximeters. We used a pulse oximeter tester device to produce stable, repetitive pulse waves with digitally adjustable R ratio and heart rate. We built a pulse oximeter and attached it to the tester device. The pulse oximeter digitized the current of its photodiode directly, without any analog signal conditioning. We varied the corner frequency of the low-pass filter in the pulse oximeter in the range of 0.66-15 Hz by software. For the tester device, the R ratio was set to R = 1.00, and the R ratio deviation measured by the pulse oximeter was monitored as a function of the corner frequency of the low-pass filter. The results revealed that lowering the corner frequency of the low-pass filter did not decrease the accuracy of the oxygen level measurements. The lowest possible value of the corner frequency of the low-pass filter is the fundamental frequency of the pulse signal. We concluded that the harmonics of the pulse signal do not contribute to the accuracy of pulse oximetry. The results achieved by the pulse oximeter tester were verified by human experiments, performed on five healthy subjects. The results of the human measurements confirmed that filtering out the harmonics of the pulse signal does not degrade the accuracy of pulse oximetry.

  10. Pulse amplitude modulated chlorophyll fluorometer

    Science.gov (United States)

    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.

  11. MgB2 thick films deposited on stainless steel substrate with Tc higher than 39K

    Institute of Scientific and Technical Information of China (English)

    LI Fen; GUO Tao; ZHANG Kai-cheng; CHEN Chin-ping; FENG Qing-rong

    2006-01-01

    Thick MgB2 (magnesium diborate) films,~10 μm,with Tc (onset)=39.4 K and Tc (zero)=39.2 K have been successfully grown on a stainless steel substrate using a technique called hybrid physical-chemical deposition (HPCVD).The deposition rate is high,~6.7 nm/s.The X-ray diffraction (XRD) indicates that it is highly (101) and c-axis oriented.The scanning electron microscope (SEM) images demonstrate that the film grown is in"island-mode".The uniform superconducting phase in the film is shown by the M-T measurement.

  12. Electromagnetic pulses bone healing booster

    Science.gov (United States)

    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.

  13. Beamline pulsing system for cyclotrons

    Science.gov (United States)

    Heikkinen, Jouko; Gustafsson, Jouni; Kivikoski, Markku; Liukkonen, Esko; Nieminen, Veikko

    A beamline pulsing system for cyclotrons is presented. The function of this system is to modify the structure of a cyclotron ion beam guided to the desired research target by a beamline. In some in-beam experiments, an adjustment of the time structure of the beam is sometimes needed. This kind of situation occurs if, for example, the life time of the target material is longer than the period corresponding to the beam frequency. In this case, the frequency of the ion pulses hitting the target is 10-21 MHz depending on the frequency of the acceleration voltage. The adjustment of the ion beam pulse frequency is carried out by a beamline deflector. Deflection is achieved by feeding a high-amplitude (10-15 kV) RF-signal between the deflection plates positioned into the beamline. This signal is generated from the cyclotron reference signal by frequency division, phase adjustment and amplification. Simulation and test results indicate that the specified deflection signal level is achieved with 1 kW of RF-power.

  14. Ion Acceleration by Short Chirped Laser Pulses

    Directory of Open Access Journals (Sweden)

    Jian-Xing Li

    2015-02-01

    Full Text Available 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 in 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.

  15. Ion Acceleration by Short Chirped Laser Pulses

    CERN Document Server

    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.

  16. Progress in time transfer by laser pulses

    Science.gov (United States)

    Li, Xin; Yang, Fu-Min

    2004-03-01

    Time transfer by laser pulses is based on the propagation of light pulses between satellite and ground clocks or between remote clocks on earth. It will realize the synchronization of these clocks with high accuracy and stability. Several experiments of the time transfer by laser pulses had been successfully carried out in some countries. These experiments validate the feasibility of the synchronization of clocks by laser pulses. The paper describes the results of these experiments. The time comparison by laser pulses between atomic clocks on aircraft and ground ones in the United States, and the LASSO and T2L2 projects in France are introduced in detail.

  17. Nonlinear Optics with Stationary Pulses of Light

    Science.gov (United States)

    André, A.; Bajcsy, M.; Zibrov, A. S.; Lukin, M. D.

    2005-02-01

    We show that the recently demonstrated technique for generating stationary pulses of light [M. Bajcsy, A. S. Zibrov, and M. D. Lukin, Nature (London)NATUAS0028-0836 426, 638 (2003)10.1038/nature02176] can be extended to localize optical pulses in all three spatial dimensions in a resonant atomic medium. This method can be used to dramatically enhance the nonlinear interaction between weak optical pulses. In particular, we show that an efficient Kerr-like interaction between two pulses can be implemented as a sequence of several purely linear optical processes. The resulting process may enable coherent interactions between single photon pulses.

  18. Pulse front adaptive optics in multiphoton microscopy

    Science.gov (United States)

    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.

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

    OpenAIRE

    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...

  20. Plasma response to transient high voltage pulses

    Indian Academy of Sciences (India)

    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.

  1. Pulse detonation engines and components thereof

    Science.gov (United States)

    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.

  2. Attosecond pulse shaping using partial phase matching

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    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

  4. CFD simulation of pulse combustion's performance

    Science.gov (United States)

    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.

  5. Atomic collisions involving pulsed positrons

    DEFF Research Database (Denmark)

    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....

  6. Repetitively pulsed material testing facility

    International Nuclear Information System (INIS)

    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.)

  7. High-power pulsed lasers

    International Nuclear Information System (INIS)

    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

  8. Ternary Chaotic Pulse Compression Sequences

    Directory of Open Access Journals (Sweden)

    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.

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

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    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

  11. A versatile programmable CAMAC random pulse generator

    International Nuclear Information System (INIS)

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

  12. Ionization of atoms by chirped attosecond pulses

    Institute of Scientific and Technical Information of China (English)

    Tan Fang; Peng Liang-You; Gong Qi-Huang

    2009-01-01

    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.

  13. Conditions for effects of radiation pulsing

    CERN Document Server

    Trinkaus, H

    2002-01-01

    The possibility of pulsing effects on radiation damage is due to differences in the delay times of relevant defect reactions and/or to the non-linear dependence of such reactions on defect production rates. Thus, significant pulsing effects require (1) proper relationships of the internal time scales of defect production and reaction to the time scales of pulsing and (2) sufficiently large pulsing induced fluctuations in relevant microstructural variables. We show that the first condition, which we quantify by a 'relative dynamic bias', is indeed fulfilled in wide ranges of the main irradiation parameters. The second condition, quantified by an 'absolute dynamic bias', is, however, found to restrict the parameter ranges of possible pulsing effects substantially. For planned spallation neutron sources and similar accelerator driven systems facilities we find, for instance, that, in the temperature range of interest, the defect yield of one pulse (controlling the absolute dynamic bias) is much too small to allo...

  14. Temporal Behavior of the Pump Pulses, Residual Pump Pulses, and THz Pulses for D2O Gas Pumped by a TEA CO2 Laser

    Science.gov (United States)

    Geng, Lijie; Zhang, Zhifeng; Zhai, Yusheng; Su, Yuling; Zhou, Fanghua; Qu, Yanchen; Zhao, Weijiang

    2016-08-01

    Temporal behavior of the pump pulses, residual pump pulses, and THz pulses for optically pumped D2O gas molecules was investigated by using a tunable TEA CO2 laser as the pumping source. The pulse profiles of pump laser pulses, residual pump pulses, and the THz output pulses were measured, simultaneously, at several different gas pressures. For THz pulse, the pulse delay between the THz pulse and the pump pulse was observed and the delay time was observed to increase from 40 to 70 ns with an increase in gas pressure from 500 to 1700 Pa. Both THz pulse broadening and compression were observed, and the pulse broadening effect transformed to the compression effect with increasing the gas pressure. For the residual pump pulse, the full width at half maximum (FWHM) of the main pulse decreased with increasing gas pressure, and the main pulse disappeared at high gas pressures. The secondary pulses were observed at high gas pressure, and the time intervals of about 518 and 435 ns were observed between the THz output pulse and the secondary residual pump pulse at the pressure of 1400 Pa and 1700 Pa, from which the vibrational relaxation time constants of about 5.45 and 5.55 μs Torr were obtained.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    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

  17. Chaotic carrier pulse position modulation communication system and method

    Science.gov (United States)

    Abarbanel, Henry D. I.; Larson, Lawrence E.; Rulkov, Nikolai F.; Sushchik, Mikhail M.; Tsimring, Lev S.; Volkovskii, Alexander R.

    2001-01-01

    A chaotic carrier pulse position modulation communication system and method is disclosed. The system includes a transmitter and receiver having matched chaotic pulse regenerators. The chaotic pulse regenerator in the receiver produces a synchronized replica of a chaotic pulse train generated by the regenerator in the transmitter. The pulse train from the transmitter can therefore act as a carrier signal. Data is encoded by the transmitter through selectively altering the interpulse timing between pulses in the chaotic pulse train. The altered pulse train is transmitted as a pulse signal. The receiver can detect whether a particular interpulse interval in the pulse signal has been altered by reference to the synchronized replica it generates, and can therefore detect the data transmitted by the receiver. Preferably, the receiver predicts the earliest moment in time it can expect a next pulse after observation of at least two consecutive pulses. It then decodes the pulse signal beginning at a short time before expected arrival of a pulse.

  18. Interpretation of Pulsed Source Experiments

    International Nuclear Information System (INIS)

    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)

  19. Pulsed UV and VUV excilamps

    Science.gov (United States)

    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 %.

  20. Design of pulse deflection magnet

    International Nuclear Information System (INIS)

    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.)

  1. Picosecond Pulse Laser Microstructuring of silicon

    Institute of Scientific and Technical Information of China (English)

    赵明; 尹钢; 朱京涛; 赵利

    2003-01-01

    We report the experimental results of picosecond pulse laser microstructuring (pulse duration 35ps, wavelength 1.06μm, repetition rate 10Hz) of silicon using the direct focusing technique. Arrays of sharp conical spikes located below the initial surface have been formed by cumulative picosecond pulsed laser irradiation of silicon in SF6. Irradiation of silicon surface in air, N2, or vacuum creates ripple-like patterns, but does not create the sharp conical spikes.

  2. Investigation of pulsed voltage limiters characteristics

    Directory of Open Access Journals (Sweden)

    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.

  3. Characteristics of pulsed discharge plasma in water

    OpenAIRE

    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...

  4. PULSE DRYING EXPERIMENT AND BURNER CONSTRUCTION

    Energy Technology Data Exchange (ETDEWEB)

    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.

  5. New pulse modulator with low switching frequency

    OpenAIRE

    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.

  6. Filters for High Rate Pulse Processing

    OpenAIRE

    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...

  7. New pulse modulator with low switching frequency

    Directory of Open Access Journals (Sweden)

    Golub V. S.

    2014-12-01

    Full Text Available 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.

  8. Pulse reversal plating of nickel alloys

    DEFF Research Database (Denmark)

    Tang, Peter Torben

    2007-01-01

    Pulse plating has previously been reported to improve the properties of nickel and nickel alloy deposits. Typically, focus has been on properties such as grain size, hardness and smoothness. When pulse plating is to be utilised for microtechnologies such as microelectromechanical systems (MEMS......), internal stress and material distribution are even more important. With baths based upon nickel chloride, and nickel and cobalt chlorides, pulse reversal plating of both pure nickel and nickel-cobalt alloys has been used to fabricate tools for microinjection moulding. Pulse reversal plating of ternary soft...

  9. Graphene in Ultrafast and Ultrastrong Laser Pulses

    Science.gov (United States)

    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.

  10. Three pulse recoupling and phase jump matching

    Science.gov (United States)

    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.

  11. Pulse front control with adaptive optics

    Science.gov (United States)

    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.

  12. Conscious Pulse II: The rules of engagement

    OpenAIRE

    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...

  13. Pulsed Single Frequency MOPA Laser Project

    Data.gov (United States)

    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...

  14. Ultrashort Laser Pulses in Biology and Medicine

    CERN Document Server

    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.

  15. Group velocity and pulse lengthening of mismatched laser pulses in plasma channels

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Carl; Benedetti, Carlo; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim

    2011-07-07

    Analytic solutions are presented to the non-paraxial wave equation describing an ultra-short, low-power, laser pulse propagating in aplasma channel. Expressions for the laser pulse centroid motion and laser group velocity are derived, valid for matched and mismatchedpropagation in a parabolic plasma channel, as well as in vacuum, for an arbitrary Laguerre-Gaussian laser mode. The group velocity of amismatched laser pulse, for which the laser spot size is strongly oscillating, is found to be independent of propagation distance andsignificantly less than that of a matched pulse. Laser pulse lengthening of a mismatched pulse owing to laser mode slippage isexamined and found to dominate over that due to dispersive pulse spreading for sufficiently long pulses. Analytic results are shown tobe in excellent agreement with numerical solutions of the full Maxwell equations coupled to the plasma response. Implications for plasmachannel diagnostics are discussed.

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

    Science.gov (United States)

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

    2016-09-01

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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    DEFF Research Database (Denmark)

    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....

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

    Energy Technology Data Exchange (ETDEWEB)

    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)

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

    Institute of Scientific and Technical Information of China (English)

    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.

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

    OpenAIRE

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

    2006-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  4. The Body as a Pulse

    Directory of Open Access Journals (Sweden)

    Flavia Liberman

    2010-01-01

    Full Text Available The body is the focus of many studies and interventions. Some paradigms conceptualize the body only in relation to its motor-sensory characteristics, while others prioritize its psychological dimensions. With the aim of contributing towards formulating other perspectives within this field, some aspects of Stanley Keleman and Regina Favre's conceptualization of the body are presented here. Starting from clinical situations during seminar groups, we can take the body to be a multifaceted multimedia pulse that is continually [de]constructed through encounters. Together with the author's clinical experiences as an occupational therapist and teacher or undergraduates, these conceptualizations serve as a guide to clinical practice that is thought out, constructed and balanced by the body, using body approaches to promote encounters molded by affections and events, in an attempt to create bodies capable of sustaining the lived intensity of experiences, and which enable self-observation, closeness to other people and production of singularities.

  5. Academic Training - Pulsed SC Magnets

    CERN Multimedia

    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...

  6. RANCHERO explosive pulsed power experiments

    CERN Document Server

    Goforth, J H; Armijo, E V; Atchison, W L; Bartos, Yu; Clark, D A; Day, R D; Deninger, W J; Faehl, R J; Fowler, C M; García, F P; García, O F; Herrera, D H; Herrera, T J; Keinigs, R K; King, J C; Lindemuth, I R; López, E; Martínez, E C; Martínez, D; McGuire, J A; Morgan, D; Oona, H; Oro, D M; Parker, J V; Randolph, R B; Reinovsky, R E; Rodríguez, G; Stokes, J L; Sena, F C; Tabaka, L J; Tasker, D G; Taylor, A J; Torres, D T; Anderson, H D; Broste, W B; Johnson, J B; Kirbie, H C

    1999-01-01

    The authors are developing the RANCHERO high explosive pulsed power (HEPP) system to power cylindrically imploding solid-density liners for hydrodynamics experiments. Their near-term goal is to conduct experiments in the regime pertinent to the Atlas capacitor bank. That is, they will attempt to implode liners of ~50 g mass at velocities approaching 15 km/sec. The basic building block of the HEPP system is a coaxial generator with a 304.8 mm diameter stator, and an initial armature diameter of 152 mm. The armature is expanded by a high explosive (HE) charge detonated simultaneously along its axis. The authors have reported a variety of experiments conducted with generator modules 43 cm long and have presented an initial design for hydrodynamic liner experiments. In this paper, they give a synopsis of their first system test, and a status report on the development of a generator module that is 1.4 m long. (6 refs).

  7. Terahertz pulsed imaging in vivo

    Science.gov (United States)

    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.

  8. Background radiation from fission pulses

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Supercapacitors and electrochemical pulse sources

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. A self-reset circuit of pulse transformer

    International Nuclear Information System (INIS)

    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. Laser system using ultra-short laser pulses

    Science.gov (United States)

    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.

  12. Maximum likelihood estimation of the attenuated ultrasound pulse

    DEFF Research Database (Denmark)

    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 ultra...

  13. Wide-range pulse-height discriminator

    Science.gov (United States)

    Cancro, C. A.; Garrahan, N. M.

    1970-01-01

    Improved pulse amplitude discriminator has discriminator level in millivolt range, permits simple adjustment over wide range, and is stable within one percent at temperatures between minus 20 degrees and plus 60 degrees C. The discriminator responds to narrow pulses /500 nsec/, draws little power /milliwatts/, and requires simple circuitry.

  14. Fast Heat Pulse Propagation by Turbulence Spreading

    DEFF Research Database (Denmark)

    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 ...

  15. Slow light pulse propagation in dispersive media

    DEFF Research Database (Denmark)

    Nielsen, Torben Roland; Mørk, Jesper; Lavrinenko, Andrei

    2009-01-01

    We present a theoretical and numerical analysis of pulse propagation in a semiconductor photonic crystal waveguide with embedded quantum dots in a regime where the pulse is subjected to both waveguide and material dispersion. The group index and the transmission are investigated by finite-differe...

  16. CLASSIFICATION OF PULSE ARC WELDING PROCESSES

    OpenAIRE

    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.

  17. Nova pulse power system description and status

    International Nuclear Information System (INIS)

    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

  18. An improved rolled strip pulse forming line

    Science.gov (United States)

    Li, Song; Qian, Bao-Liang; Yang, Han-Wu; Gao, Jing-Ming; Liu, Zhao-Xi

    2013-06-01

    The rolled strip pulse forming line (RSPFL) has advantages of compactness, portability, and long pulse achievability which could well meet the requirements of industrial application of the pulse power technology. In this paper, an improved RSPFL with an additional insulator between the grounded conductors is investigated numerically and experimentally. Results demonstrate that the jitter on the flat-top of the output voltage waveform is reduced to 3.8% due to the improved structure. Theoretical analysis shows that the electromagnetic coupling between the conductors of the RSPFL strongly influences the output voltage waveform. Therefore, the new structure was designed to minimize the detrimental effect of the electromagnetic coupling. Simulation results show that the electromagnetic coupling can be efficiently reduced in the improved RSPFL. Experimental results illustrate that the improved RSPFL, with dimensions and weight of Φ 290 × 250 mm and 16 kg, when used as a simple pulse forming line, could generate a well shaped quasi-square pulse with output power of hundreds of MW and pulse duration of 250 ns. Importantly, the improved RSPFL was successfully used as a Blumlein pulse forming line, and a 10.8 kV, 260 ns quasi-square pulse was obtained on a 2 Ω dummy load. Experiments show reasonable agreement with numerical analysis.

  19. Colliding pulse mode-locked VECSEL

    Science.gov (United States)

    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.

  20. Nanosecond pulse generators for induction linear accelerators

    International Nuclear Information System (INIS)

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

  1. Electric pulse generator with a saturable inductance

    International Nuclear Information System (INIS)

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

  2. Review of High Power Pulse Transformer Design

    Science.gov (United States)

    Zhang, Zhao; Tan, Xiaohua

    Vacuum devices generally work under high power pulse voltage of order 103 V to 106 V, and this pulse voltage could be generated by high power pulse transformer. Relatively, pulse transformer has the advantages of compact structure and excellent repetitiveness. It is expected of short rise-time, wide pulse-width and high energy transferring efficiency in most applications. Aiming at this purpose, it is feasible to select magnetic core with high permeability and high saturation magnetic flux density, use closed core and take some special measures to diminish leakage inductance in the making-process. This paper is a brief summary of high power pulse transformer design. In this paper, the principle, types and characteristics specification of high power pulse transformer are presented, and the design methods of electrical, magnetic and structure parameters are summarized. The methods of shortening rise time, diminishing droop and expanding output pulse-width (electrical parameter design), testing magnetic core materials (magnetic parameter design) and minimizing leakage inductance (structure parameter design) are emphasized.

  3. Low power arcjet thruster pulse ignition

    Science.gov (United States)

    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.

  4. Pulsed electric field inactivation in a microreactor

    NARCIS (Netherlands)

    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

  5. Observation of pulsed neutron Ramsey resonance

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Y. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba Ibaraki 305-0801 (Japan)]. E-mail: yasuhiro.masuda@kek.jp; Skoy, V. [Joint Institute for Nuclear Reasearch, 141980 Dubna, Moscow Region (Russian Federation); Ino, T. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba Ibaraki 305-0801 (Japan); Jeong, S.C. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba Ibaraki 305-0801 (Japan); Watanabe, Y. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba Ibaraki 305-0801 (Japan)

    2007-07-15

    A Ramsey resonance for pulsed neutrons was observed. The separated oscillatory fields for nuclear magnetic resonance were synchronized with a neutron pulse, and then the Ramsey resonance was observed as a function of the neutron velocity. The phase of one of the oscillatory fields was modulated as a function of the neutron time of flight for a neutron velocity measurement.

  6. Design of a Compact Pulsed Power Accelerator

    Institute of Scientific and Technical Information of China (English)

    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,

  7. Nasal pulse oximetry overestimates oxygen saturation

    DEFF Research Database (Denmark)

    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...

  8. Optimization of the LCLS Single Pulse Shutter

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Pulse interaction in nonlinear vacuum electrodynamics

    OpenAIRE

    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.

  10. Short-pulse chemical beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    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

  11. Methods for High Power EM Pulse Measurement

    Directory of Open Access Journals (Sweden)

    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.

  12. Exawatt-Zettawatt Pulse Generation and Applications

    CERN Document Server

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

    2011-01-01

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

  13. Applications of fiberoptic pulsed photothermal radiometry

    Science.gov (United States)

    Scharf, Vered; Eyal, Ophir; Katzir, Abraham

    1998-10-01

    Pulsed photothermal radiometry is a nondestructive technique for measurements of surface and subsurface thermal parameters of a wide variety of materials. A fiber optic pulsed photothermal radiometric system is constructed and its feasibility is demonstrated. The radiometric system includes a pulsed CO2 laser, an IR detector, and two IR transmitting silver halide optical fibers for delivering IR radiation to and from the sample. A weak laser pulse, absorbed by the sample, initially heats the sample surface. The time evolution of the transient emitted IR radiation is measured and analyzed. The results establish the feasibility of using the fiber optic pulsed photothermal radiometric system to measure coating thickness, to detect flaws, and to diagnose thermal damage in tissue. This fiber optic method would be useful for industrial and medical applications.

  14. Analysis of Picosecond Pulsed Laser Melted Graphite

    Science.gov (United States)

    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.

  15. Conscious Pulse II The rules of engagement

    CERN Document Server

    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.

  16. Nonlinear temporal pulse cleaning techniques and application

    Institute of Scientific and Technical Information of China (English)

    Yi; Xu; Jianzhou; Wang; Yansui; Huang; Yanyan; Li; Xiaomin; Lu; Yuxin; Leng

    2013-01-01

    Two different pulse cleaning techniques for ultra-high contrast laser systems are comparably analysed in this work.The first pulse cleaning technique is based on noncollinear femtosecond optical-parametric amplification(NOPA)and second-harmonic generation(SHG)processes.The other is based on cross-polarized wave(XPW)generation.With a double chirped pulse amplifier(double-CPA)scheme,although temporal contrast enhancement in a high-intensity femtosecond Ti:sapphire chirped pulse amplification(CPA)laser system can be achieved based on both of the techniques,the two different pulse cleaning techniques still have their own advantages and are suitable for different contrast enhancement requirements of different laser systems.

  17. Relativistic laser pulse compression in magnetized plasmas

    International Nuclear Information System (INIS)

    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

  18. Pulse distortion in single-mode fibers.

    Science.gov (United States)

    Marcuse, D

    1980-05-15

    A theory is presented of the propagation of Gaussian pulses in single-mode optical fibers by expanding the propagation constant in a Taylor series that includes the third derivative with respect to frequency. The light source is assumed to have a Gaussian spectral distribution whose width relative to the width of the Gaussian signal pulse is arbitrary. Formulas are derived for the spectrum of the ensemble average of the optical pulse, from which the shape of the average pulse itself is obtained by the fast Fourier transform. Also derived is an expression for the rms pulse width. The theory is applicable at all wavelengths including the vicinity of the zero first-order dispersion point.

  19. MOPA pulsed fiber laser for silicon scribing

    Science.gov (United States)

    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.

  20. Molecular wakes for ultrashort laser pulses

    Institute of Scientific and Technical Information of China (English)

    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.

  1. Angular Spectrum Simulation of Pulsed Ultrasound Fields

    DEFF Research Database (Denmark)

    Du, Yigang; Jensen, Henrik; Jensen, Jørgen Arendt

    2009-01-01

    The optimization of non-linear ultrasound imaging should in a first step be based on simulation, as this makes parameter studies considerably easier than making transducer prototypes. Such a simulation program should be capable of simulating non-linear pulsed fields for arbitrary transducer...... geometries for any kind of focusing and apodization. The Angular Spectrum Approach (ASA) is capable of simulating monochromatic non-linear acoustic wave propagation. However, for ultrasound imaging the time response of each specific point in space is required, and a pulsed ASA simulation with multi temporal....... The RMS error of the pulses for all points in the simulated plane is 10.9%. The good agreement between ASA and Field II simulation for the pulsed ultrasound fields obtained in this paper makes it possible to expand Field II to non-linear pulsed fields....

  2. One laser pulse generates two photoacoustic signals

    CERN Document Server

    Gao, Fei; Zheng, Yuanjin

    2016-01-01

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

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

    International Nuclear Information System (INIS)

    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)

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

    Institute of Scientific and Technical Information of China (English)

    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.

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

    CERN Document Server

    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.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Liqiang [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Chu, Tianshu, 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.

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

    Science.gov (United States)

    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.

  9. Surface-reflection-initiated pulse-contrast degradation in an optical parametric chirped-pulse amplifier.

    Science.gov (United States)

    Wang, Jing; Yuan, Peng; Ma, Jingui; Wang, Yongzhi; Xie, Guoqiang; Qian, Liejia

    2013-07-01

    We study a novel mechanism of pre-pulse generation in an optical parametric chirped-pulse amplification (OPCPA) system through an analytical approach together with numerical simulations. The acquired pre-pulses are initiated from the surface-reflection-induced modulation of the seed spectrum and occur as a consequence of high-order distortion of such modulated spectrum due to the instantaneous gain saturation effect. We demonstrate that the intensities of pre-pulses increase quadratically with the initial temporal modulation-depth of the stretched signal pulse as well as the conversion efficiency prior to substantial pump-depletion. Explicit formulas for estimating the contrast limit due to surface reflections are present. We also discuss the impact of group-velocity mismatch on the pre-pulse generation. The results of this work may deepen our cognition on the complexity of the pulse-contrast problem in OPCPA systems. PMID:23842344

  10. Procedure of Calculating the Parameters of the Inter-Pulse Period in Pulsed Arc Welding

    Science.gov (United States)

    Krampit, A. G.; Krampit, M. A.

    2016-08-01

    The procedure of calculating the parameters of the inter-pulse period such as current strength, electrode supply speed and time length is presented in the paper. Their importance for the stable arc burning is demonstrated. The authors address to the inter-pulse period parameters, influencing on the temperature of the electrode in the device, where the inter-pulse current is used for heating the electrode. The data of calculations are confirmed in the process of experiments. The appropriate parameters of pulsed arc welding with preheated electrode extension are identified; the stability of the process is tested experimentally: impulse frequency, inter-pulse period, arc voltage during the inter-pulse period, speed of electrode supply, current of the inter-pulse period.

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

    Indian Academy of Sciences (India)

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

    2014-08-01

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

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

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    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.

  14. Charged particle interaction with a chirped electromagnetic pulse

    NARCIS (Netherlands)

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

    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.

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

    Indian Academy of Sciences (India)

    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.

  16. Time shift of pulses due to dispersion slope and nonlinearity

    Energy Technology Data Exchange (ETDEWEB)

    Marcuse, D.; Menyuk, C.R.; Holzloehner, R.

    1999-12-01

    The authors show that the time delay of optical pulses traveling in long fibers is influenced by the dispersion slope and the fiber nonlinearity. Consequently, one or more new pulses that are inserted by add-drop operations into a pulse train that has already traveled a long distance may shift relative to the old pulses. This time shift delays the initial pulses more than the newly inserted ones, so that the newly inserted pulses can leave their time frames, leading to errors.

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

    DEFF Research Database (Denmark)

    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....

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

    OpenAIRE

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

    2014-01-01

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

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

    Science.gov (United States)

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

    2007-04-01

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

  20. Pulse shortening of an ultrafast VECSEL

    Science.gov (United States)

    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.

  1. Adjustable fetal phantom for pulse oximetry

    Science.gov (United States)

    Stubán, Norbert; Niwayama, Masatsugu

    2009-05-01

    As the measuring head of a fetal pulse oximeter must be attached to the head of the fetus inside the mother's uterus during labor, testing, and developing of fetal pulse oximeters in real environment have several difficulties. A fetal phantom could enable evaluation of pulse oximeters in a simulated environment without the restrictions and difficultness of medical experiments in the labor room. Based on anatomic data we developed an adjustable fetal head phantom with three different tissue layers and artificial arteries. The phantom consisted of two arteries with an inner diameter of 0.2 and 0.4 mm. An electronically controlled pump produced pulse waves in the arteries. With the phantom we investigated the sensitivity of a custom-designed wireless pulse oximeter at different pulsation intensity and artery diameters. The results showed that the oximeter was capable of identifying 4% and 2% changes in diameter between the diastolic and systolic point in arteries of over 0.2 and 0.4 mm inner diameter, respectively. As the structure of the phantom is based on reported anatomic values, the results predict that the investigated custom-designed wireless pulse oximeter has sufficient sensitivity to detect the pulse waves and to calculate the R rate on the fetal head.

  2. Spin gymnastics with selective radiofrequency pulses

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    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.

  4. Beamlet pulsed-power system

    Energy Technology Data Exchange (ETDEWEB)

    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.

  5. Technology of Pulse Power Capacitors

    Science.gov (United States)

    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.

  6. Intense Pulsed Heavy Ion Beam Technology

    Science.gov (United States)

    Masugata, Katsumi; Ito, Hiroaki

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

  7. Dynamics of laser-induced electroconvection pulses.

    Science.gov (United States)

    Giebink, N C; Johnson, E R; Saucedo, S R; Miles, E W; Vardanyan, K K; Spiegel, D R; Allen, C C

    2004-06-01

    We first report that, for planar nematic 4-methoxy-benzilidene-4-butylaniline (MBBA), the electroconvection threshold voltage has a nonmonotonic temperature dependence, with a well-defined minimum, and a slope of about -0.12 V/degrees C near room temperature at 70 Hz. Motivated by this observation, we have designed an experiment in which a weak continuous-wave absorbed laser beam with a diameter comparable to the pattern wavelength generates a locally supercritical region, or pulse, in dye-doped MBBA. Working 10-20 % below the laser-free threshold voltage, we observe a steady-state pulse shaped as an ellipse with the semimajor axis oriented parallel to the nematic director, with a typical size of several wavelengths. The pulse is robust, persisting even when spatially extended rolls develop in the surrounding region, and displays rolls that counterpropagate along the director at frequencies of tenths of Hz, with the rolls on the left (right) side of the ellipse moving to the right (left). Systematic measurements of the sample-voltage dependence of the pulse amplitude, spatial extent, and frequency show a saturation or decrease when the control parameter (evaluated at the center of the pulse) approaches approximately 0.3. We propose that the model for these pulses should be based on the theory of control-parameter ramps, supplemented with new terms to account for the advection of heat away from the pulse when the surrounding state becomes linearly unstable. The advection creates a negative feedback between the pulse size and the efficiency of heat transport, which we argue is responsible for the attenuation of the pulse at larger control-parameter values.

  8. Dynamics of laser-induced electroconvection pulses

    Science.gov (United States)

    Giebink, N. C.; Johnson, E. R.; Saucedo, S. R.; Miles, E. W.; Vardanyan, K. K.; Spiegel, D. R.; Allen, C. C.

    2004-06-01

    We first report that, for planar nematic 4-methoxy-benzilidene-4-butylaniline (MBBA), the electroconvection threshold voltage has a nonmonotonic temperature dependence, with a well-defined minimum, and a slope of about -0.12 V/° C near room temperature at 70 Hz. Motivated by this observation, we have designed an experiment in which a weak continuous-wave absorbed laser beam with a diameter comparable to the pattern wavelength generates a locally supercritical region, or pulse, in dye-doped MBBA. Working 10 20 % below the laser-free threshold voltage, we observe a steady-state pulse shaped as an ellipse with the semimajor axis oriented parallel to the nematic director, with a typical size of several wavelengths. The pulse is robust, persisting even when spatially extended rolls develop in the surrounding region, and displays rolls that counterpropagate along the director at frequencies of tenths of Hz, with the rolls on the left () side of the ellipse moving to the right (left). Systematic measurements of the sample-voltage dependence of the pulse amplitude, spatial extent, and frequency show a saturation or decrease when the control parameter (evaluated at the center of the pulse) approaches ˜0.3 . We propose that the model for these pulses should be based on the theory of control-parameter ramps, supplemented with new terms to account for the advection of heat away from the pulse when the surrounding state becomes linearly unstable. The advection creates a negative feedback between the pulse size and the efficiency of heat transport, which we argue is responsible for the attenuation of the pulse at larger control-parameter values.

  9. Modulated pulse bathymetric lidar Monte Carlo simulation

    Science.gov (United States)

    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.

  10. From reactors to long pulse sources

    International Nuclear Information System (INIS)

    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

  11. Stationary Light Pulses in Cold Atomic Media

    CERN Document Server

    Liao, Wen-Te; Peters, Thorsten; Chou, Hung-Chih; Wang, Jian-Siung; Kuan, Pei-Chen; Yu, Ite A

    2008-01-01

    Stationary light pulses (SLPs), i.e., light pulses without motion, are formed via the retrieval of stored probe pulses with two counter-propagating coupling fields. We show that there exist non-negligible hybrid Raman excitations in media of cold atoms that prohibit the SLP formation. We experimentally demonstrate a method to suppress these Raman excitations and realize SLPs in laser-cooled atoms. Our work opens the way to SLP studies in cold as well as in stationary atoms and provides a new avenue to low-light-level nonlinear optics.

  12. Analysis of multiple pulse NMR in solids

    Science.gov (United States)

    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.

  13. Laser pulse shaping for high gradient accelerators

    Science.gov (United States)

    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.

  14. Pulsed 3-Axis Vector SERF Magnetometer

    Science.gov (United States)

    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.

  15. Wuhan pulsed high magnetic field center

    OpenAIRE

    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...

  16. Ultrashort X-ray pulse science

    International Nuclear Information System (INIS)

    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

  17. Pulse propagation in the laser wakefield accelerator

    International Nuclear Information System (INIS)

    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

  18. Pulse Compression Technique of Radio Fuze

    Institute of Scientific and Technical Information of China (English)

    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.

  19. Ultrashort X-ray pulse science

    Energy Technology Data Exchange (ETDEWEB)

    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

  20. Electron trajectories in pulsed radiation fields

    International Nuclear Information System (INIS)

    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

  1. High frequency and pulse scattering physical acoustics

    CERN Document Server

    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

  2. Pulsed field gel electrophoresis a practical guide

    CERN Document Server

    Birren, Bruce

    1993-01-01

    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

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

    OpenAIRE

    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 ...

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    Konoplev, O A

    2000-01-01

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

  6. A new pulse width reduction technique for pulsed electron paramagnetic resonance spectroscopy.

    Science.gov (United States)

    Ohba, Yasunori; Nakazawa, Shigeaki; Kazama, Shunji; Mizuta, Yukio

    2008-03-01

    We present a new technique for a microwave pulse modulator that generates a short microwave pulse of approximately 1ns for use in an electron paramagnetic resonance (EPR) spectrometer. A quadruple-frequency multiplier that generates a signal of 16-20GHz from an input of 4-5GHz was employed to reduce the rise and fall times of the pulse prepared by a PIN diode switch. We examined the transient response characteristics of a commercial frequency multiplier and found that the device can function as a multiplier for pulsed signal even though it was designed for continuous wave operation. We applied the technique to a Ku band pulsed EPR spectrometer and successfully observed a spin echo signal with a broad excitation bandwidth of approximately 1.6mT using 80 degrees pulses of 1.5ns. PMID:18248828

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  10. Modeling Pulse Characteristics in Xenon with NEST

    CERN Document Server

    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.

  11. Modeling pulse characteristics in Xenon with NEST

    Science.gov (United States)

    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.

  12. The Compact Pulsed Hadron Source Construction Status

    CERN Document Server

    Wei, Jie; Cai, Jinchi; Chen, Huaibi; Cheng, Cheng; Du, Qiang; Du, Taibin; Feng, Qixi; Feng, Zhe; Gong, Hui; Guan, Xialing; Han, Xiaoxue; Huang, Tuchen; Huang, Zhifeng; Li, Renkai; Li, Wenqian; Loong, Chun-Keung; Tang, Chuanxiang; Tian, Yang; Wang, Xuewu; Xie, Xiaofeng; Xing, Qingzi; Xiong, Zhengfeng; Xu, Dong; Yang, Yigang; Zeng, Zhi; Zhang, Huayi; Zhang, Xiaozhang; Zheng, Shu-xin; Zheng, Zhihong; Zhong, Bin; Billen, James; Young, Lloyd; Fu, Shinian; Tao, Juzhou; Zhao, Yaliang; Guan, Weiqiang; He, Yu; Li, Guohua; Li, Jian; Zhang, Dong-sheng; Li, Jinghai; Liang, Tianjiao; Liu, Zhanwen; Sun, Liangting; Zhao, Hongwei; Shao, Beibei; Stovall, James

    2010-01-01

    This paper reports the design and construction status, technical challenges, and future perspectives of the proton-linac based Compact Pulsed Hadron Source (CPHS) at the Tsinghua University, Beijing, China

  13. Binary Pulse Compression Techniques for MST Radars

    Science.gov (United States)

    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.

  14. Performance of a tapered pulse tube

    Energy Technology Data Exchange (ETDEWEB)

    Swift, G.; Allen, M.; Woolan, J.J. [Cryenco Inc., Denver, CO (United States)

    1998-02-01

    In a well instrumented pulse tube refrigerator having 1,500 W of cooling power at 125 K, the authors have measured the figure of merit of a tapered pulse tube at several operating points. At operating points near the operating point for which the taper was designed, the figure of merit is 0.96. This is close to the theoretical optimum figure of merit 0.97 calculated for this pulse tube considering only two loss mechanisms: heat conduction in the metal pulse tube wall and ordinary thermoacoustic heat transport in the gas within a few thermal penetration depths of the wall. At operating points farther from the design operating point, the measured figure of merit is much lower, as streaming driven convection adds a third loss mechanism.

  15. Pulse transformer for GaAs laser

    Science.gov (United States)

    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.

  16. Propagating Characteristics of Pulsed Laser in Rain

    Directory of Open Access Journals (Sweden)

    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.

  17. Ultrashort Pulse Propagation in Nonlinear Dispersive Fibers

    Science.gov (United States)

    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

  18. Sound pulse broadening in stressed granular media.

    Science.gov (United States)

    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

  19. Observations of Radio Giant Pulses with GAVRT

    CERN Document Server

    Jones, Glenn

    2015-01-01

    Radio giant pulses provide a unique opportunity to study the pulsar radio emission mechanism in exquisite detail. Previous studies have revealed a wide range of properties and phenomena, including extraordinarily high brightness temperatures, sub-nanosecond emission features, and banded dynamic spectra. New measurements of giant pulse characteristics can help guide and test theoretical emission models. To this end, an extensive observation campaign has begun which will provide more than 500 hours on the Crab with a 34-meter antenna located in California, USA. The observations are being done as part of an educational outreach program called the Goldstone-Apple Valley Radio Telescope (GAVRT). This antenna has a novel wide bandwidth receiver which provides up to 8 GHz of instantaneous bandwidth in the range of 2.5 to 14 GHz. These observations will provide detailed information about the variability, amplitude distribution, and detailed frequency structure of radio giant pulses. In addition, a database of pulses ...

  20. Pulse radiolysis studies of model membranes

    International Nuclear Information System (INIS)

    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.)

  1. Multiphoton ionization with femtosecond laser pulses

    International Nuclear Information System (INIS)

    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

  2. The ESRF Miniature Pulsed Magnetic Field System

    Science.gov (United States)

    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.

  3. Pulse oximetry in sickle cell disease.

    Science.gov (United States)

    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

  4. High frequency group pulse electrochemical machining

    Institute of Scientific and Technical Information of China (English)

    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.

  5. Heat accumulation during pulsed laser materials processing.

    Science.gov (United States)

    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

  6. Coherent control of stationary light pulses

    Science.gov (United States)

    Zimmer, F. E.; André, A.; Lukin, M. D.; Fleischhauer, M.

    2006-08-01

    We present a detailed analysis of the recently demonstrated technique to generate quasi-stationary pulses of light [M. Bajcsy, A.S. Zibrov, M.D. Lukin, Nature (London) 426 (2003) 638] based on electromagnetically induced transparency. We show that the use of counter-propagating control fields to retrieve a light pulse, previously stored in a collective atomic Raman excitation, leads to quasi-stationary light field that undergoes a slow diffusive spread. The underlying physics of this process is identified as pulse matching of probe and control fields. We then show that spatially modulated control-field amplitudes allow us to coherently manipulate and compress the spatial shape of the stationary light pulse. These techniques can provide valuable tools for quantum nonlinear optics and quantum information processing.

  7. Pulsed laser illumination of photovoltaic cells

    Science.gov (United States)

    Yater, Jane A.; Lowe, Roland A.; Jenkins, Phillip P.; Landis, Geoffrey A.

    1995-01-01

    In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic receivers to provide remote power. Both the radio-frequency (RF) and induction FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL format.

  8. A pulsed cathodic arc spacecraft propulsion system

    Science.gov (United States)

    Neumann, P. R. C.; Bilek, M. M. M.; Tarrant, R. N.; McKenzie, D. R.

    2009-11-01

    We investigate the use of a centre-triggered cathodic arc as a spacecraft propulsion system that uses an inert solid as a source of plasma. The cathodic vacuum arc produces almost fully ionized plasma with a high exhaust velocity (>104 m s-1), giving a specific impulse competitive with other plasma or ion thrusters. A centre trigger design is employed that enables efficient use of cathode material and a high pulse-to-pulse repeatability. We compare three anode geometries, two pulse current profiles and two pulse durations for their effects on impulse generation, energy and cathode material usage efficiency. Impulse measurement is achieved through the use of a free-swinging pendulum target constructed from a polymer material. Measurements show that impulse is accurately controlled by varying cathode current. The cylindrical anode gave the highest energy efficiency. Cathode usage is optimized by choosing a sawtooth current profile. There is no requirement for an exhaust charge neutralization system.

  9. Space-time engineering with LASETRON pulses

    OpenAIRE

    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.

  10. The Dynamics of Compact Laser Pulses

    OpenAIRE

    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...

  11. The dynamics of compact laser pulses

    Science.gov (United States)

    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.

  12. Single-pulse stimulated Raman scattering spectroscopy

    CERN Document Server

    Frostig, Hadas; Natan, Adi; Silberberg, Yaron

    2010-01-01

    We demonstrate the acquisition of stimulated Raman scattering spectra with the use of a single femtosecond pulse. High resolution vibrational spectra are obtained by shifting the phase of a narrow band of frequencies in the broadband input pulse spectrum, using spectral shaping. The vibrational spectrum is resolved by examining the amplitude features formed in the spectrum after interaction with the sample. Using this technique, low frequency Raman lines (<100cm^-1) are resolved in a straightforward manner.

  13. Where do pulse oximeter probes break?

    Science.gov (United States)

    Crede, S; Van der Merwe, G; Hutchinson, J; Woods, D; Karlen, W; Lawn, J

    2014-06-01

    Pulse oximetry, a non-invasive method for accurate assessment of blood oxygen saturation (SPO2), is an important monitoring tool in health care facilities. However, it is often not available in many low-resource settings, due to expense, overly sophisticated design, a lack of organised procurement systems and inadequate medical device management and maintenance structures. Furthermore medical devices are often fragile and not designed to withstand the conditions of low-resource settings. In order to design a probe, better suited to the needs of health care facilities in low-resource settings this study aimed to document the site and nature of pulse oximeter probe breakages in a range of different probe designs in a low to middle income country. A retrospective review of job cards relating to the assessment and repair of damaged or faulty pulse oximeter probes was conducted at a medical device repair company based in Cape Town, South Africa, specializing in pulse oximeter probe repairs. 1,840 job cards relating to the assessment and repair of pulse oximeter probes were reviewed. 60.2 % of probes sent for assessment were finger-clip probes. For all probes, excluding the neonatal wrap probes, the most common point of failure was the probe wiring (>50 %). The neonatal wrap most commonly failed at the strap (51.5 %). The total cost for quoting on the broken pulse oximeter probes and for the subsequent repair of devices, excluding replacement components, amounted to an estimated ZAR 738,810 (USD $98,508). Improving the probe wiring would increase the life span of pulse oximeter probes. Increasing the life span of probes will make pulse oximetry more affordable and accessible. This is of high priority in low-resource settings where frequent repair or replacement of probes is unaffordable or impossible.

  14. Interferometry of light propagation in pulsed fields

    OpenAIRE

    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...

  15. Colliding pulse mode-locked VECSEL

    Science.gov (United States)

    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 (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.

  16. Applications of Pulse-Coupled Neural Networks

    CERN Document Server

    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

  17. Pulsed liquid microjet for microsurgical applications

    Science.gov (United States)

    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.

  18. Cold moderators for pulsed neutron sources

    International Nuclear Information System (INIS)

    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

  19. Cold moderators for pulsed neutron sources

    International Nuclear Information System (INIS)

    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

  20. Mathematical description of bacterial traveling pulses

    OpenAIRE

    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...

  1. Mathematical Description of Bacterial Traveling Pulses

    OpenAIRE

    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 ...

  2. Mathematical description of bacterial traveling pulses

    OpenAIRE

    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 ...

  3. Classical Dynamics of Free Electromagnetic Laser Pulses

    OpenAIRE

    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...

  4. Future opportunities with pulsed neutron sources

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, A.D. [Rutherford Appleton Lab., Chilton (United Kingdom)

    1996-05-01

    ISIS is the world`s most powerful pulsed spallation source and in the past ten years has demonstrated the scientific potential of accelerator-driven pulsed neutron sources in fields as diverse as physics, earth sciences, chemistry, materials science, engineering and biology. The Japan Hadron Project gives the opportunity to build on this development and to further realize the potential of neutrons as a microscopic probe of the condensed state. (author)

  5. Magnetic Linear Birefringence Measurements Using Pulsed Fields

    CERN Document Server

    Berceau, Paul; Battesti, Remy; Rizzo, Carlo

    2011-01-01

    In this paper we present the accomplishment of the further step towards the vacuum magnetic birefringence measurement based on pulsed fields. After describing our BMV experiment, we report the calibration of our apparatus with nitrogen gas and we discuss the precision of our measurement giving a detailed error budget. Our best present vacuum sensitivity is 2.1x 10^-19 T^-2 per 5 ms magnetic pulse. We finally discuss the perspectives to reach our final goal.

  6. Pulsed electric field inactivation in a microreactor

    OpenAIRE

    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 are much less affected. At the moment, the PEF process faces several challenges, to which microtechnology could be an aid. The small electrode distance in microtechnological reactors enables the use ...

  7. Long pulse operation on Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    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.

  8. Long pulse operation on Tore Supra

    International Nuclear Information System (INIS)

    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

  9. Pulsed uv nitrogen laser: dynamical behavior

    International Nuclear Information System (INIS)

    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

  10. Attosecond pulse shaping using partial phase matching

    OpenAIRE

    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.

  11. Chirped-pulse oscillators: a unified standpoint

    OpenAIRE

    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.

  12. Pulse Clarithromycin Therapy In Severe ACNE Vulgaris

    Directory of Open Access Journals (Sweden)

    Rathi Sanjay K

    2002-01-01

    Full Text Available Three patients with severe acne vulgaris, not responding with long courses of doxycycline, minocycline and erythromycin were given oral clarithromycin in pulsed regimen. The patients were given 7 days course of clarithromycin 250mg twice daily, which was repeated after a gap of 10 days. Such 3 courses were given. The lesions responded significantly. No significant side effect was noted. Pulse clarithromycin therapy seems to be a good alternative and effective tool in the management of severe acne vulgaris.

  13. Double regenerative amplification of picosecond pulses

    Science.gov (United States)

    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.

  14. Laser pulse shaping with liquid crystals

    OpenAIRE

    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...

  15. Study of terahertz pulses at an edge

    Institute of Scientific and Technical Information of China (English)

    Zaijun Xi; Xiaohan Yu; Tiqiao Xiao

    2008-01-01

    The propagation behaviour of terahertz (THz) pulses at an edge is characterized. The phenomenon that the amplitude oscillates periodically in the frequency spectrum is similar to Young's interference, if the absorption effect is neglected. The oscillation cycle is shorter for a thicker sample. THz pulses at anedge are an alyzed by the broadband Huygens-Fresnel diffraction integral. The experimental results are in agreement with the simulation results approximately. The simulation errors are also analyzed.

  16. Assessment and mitigation of electromagnetic pulse (EMP) impacts at short-pulse laser facilities

    International Nuclear Information System (INIS)

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

  17. 90 mJ parametric chirped pulse amplification of 10 fs pulses.

    Science.gov (United States)

    Tavella, Franz; Marcinkevicius, Andrius; Krausz, Ferenc

    2006-12-25

    We demonstrate the amplification of broadband pulses from a Ti:Sapphire oscillator by non-collinear optical parametric chirped-pulse amplification technique in a type-I BBO crystal to energies of 90 mJ. Partial compression of the amplified pulses is demonstrated down to a 10 fs duration. These parameters come in combination with good spatial quality and focusability of the amplified beam.

  18. Increasing pulse wave velocity in a realistic cardiovascular model does not increase pulse pressure with age

    OpenAIRE

    Mohiuddin, Mohammad W.; Rihani, Ryan J.; Laine, Glen A.; Quick, Christopher M.

    2012-01-01

    The mechanism of the well-documented increase in aortic pulse pressure (PP) with age is disputed. Investigators assuming a classical windkessel model believe that increases in PP arise from decreases in total arterial compliance (Ctot) and increases in total peripheral resistance (Rtot) with age. Investigators assuming a more sophisticated pulse transmission model believe PP rises because increases in pulse wave velocity (cph) make the reflected pressure wave arrive earlier, augmenting systol...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-07-15

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

  20. Pulse Compression of Phase-matched High Harmonic Pulses from a Time-Delay Compensated Monochromator

    Directory of Open Access Journals (Sweden)

    Ito Motohiko

    2013-03-01

    Full Text Available Pulse compression of single 32.6-eV high harmonic pulses from a time-delay compensated monochromator was demonstrated down to 11±3 fs by compensating the pulse front tilt. The photon flux was intensified up to 5.7×109 photons/s on target by implementing high harmonic generation under a phase matching condition in a hollow fiber used for increasing the interaction length.

  1. 90 mJ parametric chirped pulse amplification of 10 fs pulses.

    Science.gov (United States)

    Tavella, Franz; Marcinkevicius, Andrius; Krausz, Ferenc

    2006-12-25

    We demonstrate the amplification of broadband pulses from a Ti:Sapphire oscillator by non-collinear optical parametric chirped-pulse amplification technique in a type-I BBO crystal to energies of 90 mJ. Partial compression of the amplified pulses is demonstrated down to a 10 fs duration. These parameters come in combination with good spatial quality and focusability of the amplified beam. PMID:19532173

  2. Investigating Pulsed Discharge Polarity Employing Solid-State Pulsed Power Electronics

    OpenAIRE

    Davari, Pooya; Zare, Firuz; Blaabjerg, Frede

    2015-01-01

    Power electronics technique has become a key technology in solid-state pulsed power supplies. Since pulsed power applications have been matured and found its way into many industrial applications, moving toward energy efficiency is gaining much more interest. Therefore, finding an optimum operation condition plays an important role in maintaining the desired performance. Investigating the system parameters contributed to the generated pulses is an effective way in improving the system perform...

  3. Interaction between two stopped light pulses

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yi-Hsin, E-mail: yhchen920@gmail.com; Lee, Meng-Jung, E-mail: yhchen920@gmail.com; Hung, Weilun, E-mail: yhchen920@gmail.com; Yu, Ite A., E-mail: yu@phys.nthu.edu.tw [Department of Physics and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, Ying-Cheng [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan and Department of Physics and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, Yong-Fan [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2014-03-05

    The efficiency of a nonlinear optical process is proportional to the interaction time. We report a scheme of all-optical switching based on two motionless light pulses via the effect of electromagnetically induced transparency. One pulse was stopped as the stationary light pulse (SLP) and the other was stopped as stored light. The time of their interaction via the medium can be prolonged and, hence, the optical nonlinearity is greatly enhanced. Using a large optical density (OD) of 190, we achieved a very long interaction time of 6.9 μs. This can be analogous to the scheme of trapping light pulses by an optical cavity with a Q factor of 8×10{sup 9}. With the approach of using moving light pulses in the best situation, a switch can only be activated at 2 photons per atomic absorption cross section. With the approach of employing a SLP and a stored light pulse, a switch at only 0.56 photons was achieved and the efficiency is significantly improved. Moreover, the simulation results are in good agreement with the experimental data and show that the efficiency can be further improved by increasing the OD of the medium. Our work advances the technology in quantum information manipulation utilizing photons.

  4. The hydrodynamic behaviour of a pulsed column

    International Nuclear Information System (INIS)

    Holdup, droplet size and continuous-phase backmixing were measured in a 72 mm i.d. pulsed perforated-plate column. The contactor was operated using the system 2 M HNO3-30% TBP/OP. Pulse amplitude, frequency and both phase flow rates were varied over a wide range of values although the column was maintained in the continuous dispersion region. Dispersed-phase holdup appeared to pass through a minimum at a constant pulse velocity corresponding to the onset of continuous dispersion type operation. The value of this minimum varied linearly with the dispersed-phase flow rate. Measurements of holdup were correlated using the slip velocity concept, modified to allow for droplet coalescence. Values of the Sauter-mean droplet diameter were found to vary with the pulse velocity and holdup. It was shown that the ratio of the characteristic droplet velocity in a pulsed perforated-plate column to that in a spray column as derived from the correlation of Hu and Kintner is a function of the pulse velocity and holdup. This led to an expression which correlated the droplet size data with negligible error. Continuous-phase back mixing was found to increase with amplitude; frequency and dispersed-phase flow rate. The effect of the continuous-phase flow rate was variable. At low values, increasing the phase velocity reduced back mixing while at high values, an increase in the phase velocity had the reverse effect

  5. Hamiltonian Framework for Short Optical Pulses

    Science.gov (United States)

    Amiranashvili, Shalva

    Physics of short optical pulses is an important and active research area in nonlinear optics. In this Chapter we theoretically consider the most extreme representatives of short pulses that contain only several oscillations of electromagnetic field. Description of such pulses is traditionally based on envelope equations and slowly varying envelope approximation, despite the fact that the envelope is not "slow" and, moreover, there is no clear definition of such a "fast" envelope. This happens due to another paradoxical feature: the standard (envelope) generalized nonlinear Schrödinger equation yields very good correspondence to numerical solutions of full Maxwell equations even for few-cycle pulses, the thing that should not be.In what follows we address ultrashort optical pulses using Hamiltonian framework for nonlinear waves. As it appears, the standard optical envelope equation is just a reformulation of general Hamiltonian equations. In a sense, no approximations are required, this is why the generalized nonlinear Schrödinger equation is so effective. Moreover, the Hamiltonian framework contributes greatly to our understanding of "fast" envelopes, ultrashort solitons, stability and radiation of optical pulses. Even the inclusion of dissipative terms is possible making the Hamiltonian approach an universal theoretical tool also in extreme nonlinear optics.

  6. Electrostatic Changes Observed with Narrow Bipolar Pulses

    Science.gov (United States)

    Karunarathne, S.; Marshall, T. C.; Stolzenburg, M.; Karunarathna, N.

    2015-12-01

    Narrow bipolar pulses (NBPs) or compact intracloud discharges are impulsive discharges that are considered to be the strongest natural emitters in the HF radio band; they usually occur at high altitudes in some thunderstorms. In the summer of 2011, we collected E-change data with wideband flat-plate antennas (0.16 Hz - 2.5 MHz) at ten stations covering an area of nearly 70 km x 100 km in and around Kennedy Space Center, Florida, USA. On one thunderstorm day, 14 August 2011, we detected 226 positive NBPs, and some observations of these pulses were published in Karunarathne et al. [2015, JGR-atmospheres]. Of these 226 NBPs, 50 (22.1 %) occurred within 10 km horizontally of at least one sensor. All of these closer sensors show electrostatic changes associated with corresponding NBPs, with a net electrostatic change in the main bipolar pulse and with a slower electrostatic change after the bipolar pulse that seems similar to short continuing current immediately after some cloud-to-ground return strokes. Although NBPs have been considered as short duration pulses (10 - 20 microseconds), the electrostatic changes after the main bipolar pulse ranged from 0.7 ms to 34 ms and associated charge moments were calculated. The total duration of the electrostatic E-change was strongly dependent on the distance to the sensors. In this presentation, we will present data for these electrostatic changes, some statistics, and physical background and reasoning for the electrostatic changes.

  7. Pulse shortening of an ultrafast VECSEL

    Science.gov (United States)

    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 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. Pulse profile stability of the Crab pulsar

    Institute of Scientific and Technical Information of China (English)

    Chetana Jain; Biswajit Paul

    2011-01-01

    We present an X-ray timing analysis of the Crab pulsar,PSR B0531+21,using archival RXTE data.We have investigated the stability of the Crab pulse profile,in soft (2-20keV) and hard (30-100keV) X-ray energies,over the last decade of RXTE operation.The analysis includes measurement of the separation between the two pulse peaks and the intensity and widths of the two peaks.We did not find any significant time dependency in the pulse shape.The two peaks have been stable in phase,intensity and width for the last ten years.The first pulse is relatively stronger at soft X-rays.The first pulse peak is narrower than the second peak in both soft and hard X-ray energies.Both the peaks show a slow rise and a steeper fall.The ratio of the pulsed photons in the two peaks is also constant in time.

  9. Pulsed neutron sources for epithermal neutrons

    International Nuclear Information System (INIS)

    It is shown how accelerator based neutron sources, giving a fast neutron pulse of short duration compared to the neutron moderation time, promise to open up a new field of epithermal neutron scattering. The three principal methods of fast neutron production: electrons, protons and fission boosters will be compared. Pulsed reactors are less suitable for epithermal neutrons and will only be briefly mentioned. The design principle of the target producing fast neutrons, the moderator and reflector to slow them down to epithermal energies, and the cell with its beam tubes and shielding will all be described with examples taken from the new Harwell electron linac to be commissioned in 1978. A general comparison of pulsed neutron performance with reactors is fraught with difficulties but has been attempted. Calculation of the new pulsed source fluxes and pulse widths is now being performed but we have taken the practical course of basing all comparisons on extrapolations from measurements on the old 1958 Harwell electron linac. Comparisons for time-of-flight and crystal monochromator experiments show reactors to be at their best at long wavelengths, at coarse resolution, and for experiments needing a specific incident wavelength. Even existing pulsed sources are shown to compete with the high flux reactors in experiments where the hot neutron flux and the time-of-flight methods can be best exploited. The sources under construction can open a new field of inelastic neutron scattering based on energy transfer up to an electron volt and beyond

  10. Modified pulse shapes for effective neural stimulation

    Directory of Open Access Journals (Sweden)

    Lorenz eHofmann

    2011-09-01

    Full Text Available Electrical stimulation of neuronal structures is used as treatment of many neu- rological disorders, e.g. for the treatment of Parkinsons disease via deep brain stimulation. To reduce side effects, to avoid tissue or electrode damage and to increase battery lifetimes, an effective but gentle electrical stimulation is of prime importance. We study different modified pulse shapes for application in deep brain stimulation with respect to their efficiency to initiate neuronal activity. Numeri- cal simulations of two mathematical neuron models are performed to investigate the effectiveness of different modified pulse shapes. According to our results, the considered pulse shapes show a considerably increased efficiency in terms of both activation and entrainment of neural activity. We find that the introduction of a gap of specific and optimized duration in a biphasic pulse and the reversal of the stan- dard pulse phase order yield stimulation protocols that may increase the efficiency and therefore reduce the energy consumption of stimulation. The improvements are achieved only by simple modifications of existing stimulation techniques. The modification of the pulse shapes results in an improvement of up to 50% for both the activation of resting neurons and the entrainment of bursting neurons.

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

    Science.gov (United States)

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

    2016-11-01

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

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

    CERN Document Server

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

    2015-01-01

    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. (2005) empirical pulse model. This signal is overlaid by a fainter, three-peaked signal that can be modeled by an empirical wave-like function (Hakkila and Preece, 2014): 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...

  13. Plant N capture from pulses: effects of pulse size, growth rate, and other soil resources.

    Science.gov (United States)

    James, J J; Richards, J H

    2005-08-01

    In arid ecosystems, the ability to rapidly capture nitrogen (N) from brief pulses is expected to influence plant growth, survival, and competitive ability. Theory and data suggest that N capture from pulses should depend on plant growth rate and availability of other limiting resources. Theory also predicts trade-offs in plant stress tolerance and ability to capture N from different size pulses. We injected K15NO3, to simulate small and large N pulses at three different times during the growing season into soil around the co-dominant Great Basin species Sarcobatus vermiculatus, Chrysothamnus nauseosus ssp. consimilis, and Distichlis spicata. Soils were amended with water and P in a partial factorial design. As predicted, all study species showed a comparable decline in N capture from large pulses through the season as growth rates slowed. Surprisingly, however, water and P availability differentially influenced the ability of these species to capture N from pulses. Distichlis N capture increased up to tenfold with water addition while Chrysothamnus N capture increased up to threefold with P addition. Sarcobatus N capture was not affected by water or P availability. Opposite to our prediction, Sarcobatus, the most stress tolerant species, captured less N from small pulses but more N from large pulses relative to the other species. These observations suggest that variation in N pulse timing and size can interact with variable soil water and P supply to determine how N is partitioned among co-existing Great Basin species.

  14. A Marx generator based high voltage high current pulsed power supply with variable pulse width

    International Nuclear Information System (INIS)

    A high voltage pulse power supply using Marx generator with solid-state switches is proposed in this paper. An IGBT based 10 stage Marx bank generator has been designed and developed. A -10 kV /100 A high voltage pulse with a variable pulse width from 100 μS to 1 ms yielding a peak power of 1 mega watt was generated. The 10 cell generator is assembled over a FRP structure where each cell consists of a charging IGBT, a discharging IGBT, a capacitor and a freewheeling diode. The modular design proposed allows cascading of similar structures to generate higher voltages. A unique compact scheme based on pulse transformer is used to drive both the charging and the discharging IGBTs. Two numbers of pulse transformers (one for charging pulse and another for discharging pulse) were designed and developed. Both pulse transformers have a single primary and multiple numbers of secondaries, one for each cell with required high voltage isolation. They are excited with high frequency inverters to generate isolated control supply and firing pulse for IGBT switching. The paper discusses the design and construction of the Marx generator and its operation. (author)

  15. Diode-Pumped Nanosecond Pulsed Laser with Pulse-Transmission-Mode Q-Switch

    Institute of Scientific and Technical Information of China (English)

    CHEN Fei; HUO Yu-Jing; HE Shu-Fang; FENG Li-Chun

    2001-01-01

    Q-switched pulses at 1.064μm with a peak power of 5.02kW and a pulse width of2.8ns were obtained which were pumped by a 1 W laser diode on the Nd:YVO4 microchip at the 1 kHz repetition rate. These values were achieved by combining the techniques of aconsto-optic Q-switching and electro-optic pulse-transmission-mode Q-switching. The temporal characteristics of the pulses were analysed numerically. The experimental results are shown to be in good agreement with theoretical predictions.

  16. Pulse-shaping mechanism in colliding-pulse mode-locked laser diodes

    DEFF Research Database (Denmark)

    Bischoff, Svend; Sørensen, Mads Peter; Mørk, J.;

    1995-01-01

    The large signal dynamics of passively colliding pulse mode-locked laser diodes is studied. We derive a model which explains modelocking via the interplay of gain and loss dynamics; no bandwidth limiting element is necessary for pulse formation. It is found necessary to have both fast and slow...... absorber dynamics to achieve mode-locking. Significant chirp is predicted for pulses emitted from long lasers, in agreement with experiment. The pulse width shows a strong dependence on both cavity and saturable absorber length. (C) 1995 American Institute of Physics....

  17. Pulse oximetry: fundamentals and technology update

    Directory of Open Access Journals (Sweden)

    Nitzan M

    2014-07-01

    Full Text Available Meir Nitzan,1 Ayal Romem,2 Robert Koppel31Department of Physics/Electro-Optics, Jerusalem College of Technology, Jerusalem, Israel; 2Pulmonary Institute, Shaare Zedek Medical Center, Jerusalem, Israel; 3Neonatal/Perinatal Medicine, Cohen Children's Medical Center of New York/North Shore-LIJ Health System, New Hyde Park, NY, United StatesAbstract: Oxygen saturation in the arterial blood (SaO2 provides information on the adequacy of respiratory function. SaO2 can be assessed noninvasively by pulse oximetry, which is based on photoplethysmographic pulses in two wavelengths, generally in the red and infrared regions. The calibration of the measured photoplethysmographic signals is performed empirically for each type of commercial pulse-oximeter sensor, utilizing in vitro measurement of SaO2 in extracted arterial blood by means of co-oximetry. Due to the discrepancy between the measurement of SaO2 by pulse oximetry and the invasive technique, the former is denoted as SpO2. Manufacturers of pulse oximeters generally claim an accuracy of 2%, evaluated by the standard deviation (SD of the differences between SpO2 and SaO2, measured simultaneously in healthy subjects. However, an SD of 2% reflects an expected error of 4% (two SDs or more in 5% of the examinations, which is in accordance with an error of 3%–4%, reported in clinical studies. This level of accuracy is sufficient for the detection of a significant decline in respiratory function in patients, and pulse oximetry has been accepted as a reliable technique for that purpose. The accuracy of SpO2 measurement is insufficient in several situations, such as critically ill patients receiving supplemental oxygen, and can be hazardous if it leads to elevated values of oxygen partial pressure in blood. In particular, preterm newborns are vulnerable to retinopathy of prematurity induced by high oxygen concentration in the blood. The low accuracy of SpO2 measurement in critically ill patients and newborns

  18. Pulse combustion: an assessment of opportunities for increased efficiency

    Energy Technology Data Exchange (ETDEWEB)

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

    1984-12-01

    The results of a literature review on pulse combustion are discussed. Current, near-future, and potential opportunities for pulse combustion applications are summarized, and the barriers to developing and using pulse combustion technology are discussed, along with research and development needs. Also provided are the proceedings of a pulse combustion workshop held in May, 1984 in Seattle, Washington. (LEW)

  19. Theoretical analysis of pulse modulation of semiconductor lasers

    Energy Technology Data Exchange (ETDEWEB)

    Xu Baoxi; Zhan Yushu; Guo Siji

    1987-05-01

    Rate equations of Gaussian shape pulse modulated semiconductor lasers are solved by Runge--Kutta method, and the results are analyzed. The formulae for calculating the delay time, pulse width of laser pulse and maximum bit-rate of Gaussian shape pulse modulation are derived. The experimental results of modulation pattern effects are given.

  20. Ultra-short pulse free electron laser oscillators

    OpenAIRE

    Blau, J; Wong, R.K.; Colson, W.B.

    1995-01-01

    An RF linear accelerator can produce ultra-short electron pulses on the order of a picosecond. In a long wavelength FEL, the pulse length can be much less than the slippage distance. Simulations show the effects of such short pulses on weak-field gain, saturated power, and optical pulse structure.

  1. Loudness of tone pulses in a free field

    DEFF Research Database (Denmark)

    Poulsen, Torben

    1981-01-01

    Investigations of temporal loudness summation of tone pulses have been performed. The investigations comprised equal loudness determinations between pairs of tone pulses with a duration ratio of 1:2, and threshold determinations of the same tone pulses. Pulse durations ranged from 5 to 640 ms. Th...

  2. Broadening and Amplification of an Infrared Femtosecond Pulse for Optical Parametric Chirped-Pulse Amplification

    Institute of Scientific and Technical Information of China (English)

    WANG He-Lin; YANG Ai-Jun; LENG Yu-Xin

    2011-01-01

    A high-average-power diode-pumped narrowband regenerative chirped pulse amplifier is developed using the thin-rod Nd:YAG laser architecture for optical parametric chirped-pulse amplification (OPCPA).The effect of the etalons on the amplified pulse in the regenerative cavity is studied experimentally and theoretically.By inserting glass etalons of thickness 1 mm and 5 mm into the regenerative cavity,the pre-stretching pulse from an (O)ffner stretcher is further broadened to above 200ps,which matches the amplification windows of the signal pulses in OPCPA and is suitable for use as a pump source in the OPCPA system.The bandwidth of the amplified pulse is 1.5 nm,and an output energy of 2mJ is achieved at a repetition rate of 10 Hz.Optical parametric chirped pulse amplification (OPCPA)[1-4] has attracted a great deal of attention as the most promising technique for generating ultrashort ultrahigh-peak-power laser pulses because of its very broad gain bandwidth,negligible thermal load on the nonlinear crystal,and extremely high singlepass gain as compared to amplifiers based on laser gain media.For efficient amplification and high fidelity of dispersion compensation in OPCPA,a femtosecond seed pulse is first stretched to several tens of picoseconds with a bulk grating stretcher or a fiber stretcher.%A high-average-power diode-pumped narrowband regenerative chirped pulse amplifier is developed using the thin-rod Nd:YAG laser architecture for optical parametric chirped-pulse amplification (OPCPA). The effect of the etalons on the amplified pulse in the regenerative cavity is studied experimentally and theoretically. By inserting glass etalons of thickness 1 mm and 5 mm into the regenerative cavity, the pre-stretching pulse from an (O)finer stretcher is further broadened to above 200 ps, which matches the amplification windows of the signal pulses in OPCPA and is suitable for use as a pump source in the OPCPA system. The bandwidth of the amplified pulse is 1.5 nm, and an

  3. High order coherent control sequences of fat pulses

    CERN Document Server

    Pasini, S; Uhrig, G S

    2010-01-01

    We analyze the performance of sequences of fat pulses of various lengths and shapes for dynamic decoupling and we compare it with that of sequences of ideal, instantaneous pulses. The use of second order, shaped pulses represents a significant improvement. Non-equidistant sequences characterized by pulse durations scaled proportional to the duration T of the sequence strikingly outperform the sequences with pulses of constant length for small T. Interestingly, for longer durations sequences of pulses of substantial length are found to suppress dephasing better than sequences of ideal pulses.

  4. Pulsed energy storage antennas for ionospheric modification

    Directory of Open Access Journals (Sweden)

    R. F. Wuerker

    2005-01-01

    Full Text Available Interesting, "new", very high peak-power pulsed radio frequency (RF antennas have been assembled at the HIPAS Observatory (Alaska, USA and also at the University of California at Los Angeles (UCLA, USA; namely, a pair of quarter wavelength (λ/4 long cylindrical conductors separated by a high voltage spark gap. Such a combination can radiate multi-megawatt RF pulses whenever the spark gap fires. The antenna at HIPAS is 53m long (λ/2 with a central pressurized SF6 spark gap. It is mounted 5 meters (λ/21 above a ground plane. It radiates at 2.85MHz. The two antenna halves are charged to ± high voltages by a Tesla coil. Spark gap voltages of 0.4 MV (at the instant of spark gap closure give peak RF currents of ~1200A which correspond to ~14 MW peak total radiated power, or ~56 MW of Effective Radiated Power (ERP. The RF pulse train is initially square, decaying exponentially in time with Qs of ~50. Two similar but smaller 80-MHz antennas were assembled at UCLA to demonstrate their synchronization with a pulsed laser which fired the spark gaps in the two antennas simultanoeously. These experiments show that one can anticipate a pulsed array of laser synchronized antennas having a coherent Effective Radiated Power (ERP>10GW. One can even reconsider a pulse array radiating at 1.43MHz which corresponds to the electron gyrofrequency in the Earth's magnetic field at ~200km altitude. These "new" pulsed high power antennas are hauntingly similar to the ones used originally by Hertz (1857-1894 during his (1886-1889 seminal verifications of Maxwell's (1864 theory of electrodynamics.

  5. Long-pulsed dye laser vs. intense pulsed light for the treatment of facial telangiectasias: a randomized controlled trial

    DEFF Research Database (Denmark)

    Nymann, Peter; Hedelund, Lene; Haedersdal, M

    2010-01-01

    This study aims to compare the efficacy and adverse effects of long-pulsed dye laser (LPDL) and intense pulsed light (IPL) in the treatment of facial telangiectasias.......This study aims to compare the efficacy and adverse effects of long-pulsed dye laser (LPDL) and intense pulsed light (IPL) in the treatment of facial telangiectasias....

  6. Compressive spectrum sensing of radar pulses based on photonic techniques.

    Science.gov (United States)

    Guo, Qiang; Liang, Yunhua; Chen, Minghua; Chen, Hongwei; Xie, Shizhong

    2015-02-23

    We present a photonic-assisted compressive sampling (CS) system which can acquire about 10(6) radar pulses per second spanning from 500 MHz to 5 GHz with a 520-MHz analog-to-digital converter (ADC). A rectangular pulse, a linear frequency modulated (LFM) pulse and a pulse stream is respectively reconstructed faithfully through this system with a sliding window-based recovery algorithm, demonstrating the feasibility of the proposed photonic-assisted CS system in spectral estimation for radar pulses.

  7. Propagation of ultrashort pulsed beams in dispersive media

    Institute of Scientific and Technical Information of China (English)

    刘志军; 吕百达

    2003-01-01

    Starting from the Rayleigh diffraction integral, the propagation equation of ultrashort pulsed beams in dispersive media is derived without making the paraxial approximation and slowly varying envelope approximation (SVEA). The spatiotemporal properties of ultrashort pulsed beams in dispersive media, such as spectrum redshifting, narrowing and pulse distortion are illustrated with pulsed Gaussian beams. It is stressed that the "antibeam" behaviour of ultrashort pulsed beams can be avoided, if a suitable truncation function is chosen.

  8. Inertial confinement fusion driven by long wavelength electromagnetic pulses

    Institute of Scientific and Technical Information of China (English)

    Baifei; Shen; Xueyan; Zhao; Longqing; Yi; Wei; Yu; Zhizhan; Xu

    2013-01-01

    A method for inertial confinement fusion driven by powerful long wavelength electromagnetic pulses(EMPs), such as CO2 laser pulses or high power microwave pulses, is proposed. Due to the high efficiency of generating such long wavelength electromagnetic pulses, this method is especially important for the future fusion electricity power. Special fuel targets are designed to overcome the shortcomings of the long wavelength electromagnetic pulses.

  9. Liquid-xenon detector under the intensive pulse irradiation conditions

    Science.gov (United States)

    Kirsanov, M. A.

    2016-02-01

    The effect of intense pulsed irradiation on the operation of the liquid xenon spectrometer was studied. The ionization chamber filled with liquid xenon was irradiated by bremsstrahlung pulses of the microtron. The pulse repetition rate was 400 Hz. The absorbed dose ranged from 10-7 to 0.1 Gy per pulse. Stable operation of the liquid xenon spectrometer in the intervals between the pulses of the accelerator was shown for a long time.

  10. Injection locked oscillator system for pulsed metal vapor lasers

    Science.gov (United States)

    Warner, Bruce E.; Ault, Earl R.

    1988-01-01

    An injection locked oscillator system for pulsed metal vapor lasers is disclosed. The invention includes the combination of a seeding oscillator with an injection locked oscillator (ILO) for improving the quality, particularly the intensity, of an output laser beam pulse. The present invention includes means for matching the first seeder laser pulses from the seeding oscillator to second laser pulses of a metal vapor laser to improve the quality, and particularly the intensity, of the output laser beam pulse.

  11. Reducing the beam current in Linac4 in pulse to pulse mode.

    CERN Document Server

    Lallement, JB; CERN. Geneva. BE Department

    2009-01-01

    In order to deliver different beam intensities to users, we studied the possibility of varying the Linac4 beam current at PS Booster injection in pulse to pulse mode. This report gives the possible configurations of Linac4 Low and Medium Energy Beam Transport lines (LEBT and MEBT) that lead to a consistent current reduction.

  12. Investigating Pulsed Discharge Polarity Employing Solid-State Pulsed Power Electronics

    DEFF Research Database (Denmark)

    Davari, Pooya; Zare, Firuz; Blaabjerg, Frede

    2015-01-01

    Power electronics technique has become a key technology in solid-state pulsed power supplies. Since pulsed power applications have been matured and found its way into many industrial applications, moving toward energy efficiency is gaining much more interest. Therefore, finding an optimum operation...

  13. Increase of pulse power of power supply systems of induction linacs with current pulse magnettic compression

    International Nuclear Information System (INIS)

    A powerful three section magnetic pulse generator of a nanosecond range designed for supply of a small-sectioned sccelerating structure up to GW units is developed. The pumping generator is mounted using the TTI2500/50 pulsed hydrogen thyratron according to the sections of magnetic compression. 2 refs.; 2 figs.; 1 tab

  14. Dynamic characterization and amplification of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers

    DEFF Research Database (Denmark)

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

    2013-01-01

    We show a first-time demonstration of amplification of 400 fs pulses in a fiber optical parametric amplifier. The 400 fs signal is stretched in time, amplified by 26 dB and compressed back to 500 fs. A significant broadening of the pulses is experimentally shown due to dispersion and limited gain...

  15. Nanoplasmonic generation of ultrashort EUV pulses

    Science.gov (United States)

    Choi, Joonhee; Lee, Dong-Hyub; Han, Seunghwoi; Park, In-Yong; Kim, Seungchul; Kim, Seung-Woo

    2012-10-01

    Ultrashort extreme-ultraviolet (EUV) light pulses are an important tool for time-resolved pump-probe spectroscopy to investigate the ultrafast dynamics of electrons in atoms and molecules. Among several methods available to generate ultrashort EUV light pulses, the nonlinear frequency upconversion process of high-harmonic generation (HHG) draws attention as it is capable of producing coherent EUV pulses with precise control of burst timing with respect to the driving near-infrared (NIR) femtosecond laser. In this report, we present and discuss our recent experimental data obtained by the plasmon-driven HHG method that generate EUV radiation by means of plasmonic nano-focusing of NIR femtosecond pulses. For experiment, metallic waveguides having a tapered hole of funnel shape inside were fabricated by adopting the focused-ion-beam process on a micro-cantilever substrate. The plasmonic field formed within the funnelwaveguides being coupled with the incident femtosecond pulse permitted intensity enhancement by a factor of ~350, which creates a hot spot of sub-wavelength size with intensities strong enough for HHG. Experimental results showed that with injection of noble gases into the funnel-waveguides, EUV radiation is generated up to wavelengths of 32 nm and 29.6 nm from Ar and Ne gas atoms, respectively. Further, it was observed that lower-order EUV harmonics are cut off in the HHG spectra by the tiny exit aperture of the funnel-waveguide.

  16. Numerical Simulation of Pulse Shortening in RBWOs

    Institute of Scientific and Technical Information of China (English)

    GONG Yu-bin; ZHANG Zhang; WANG Wen-xiang; MENG Fan-bao; FAN Zhi-kai; HUANG Min-zhi

    2005-01-01

    Pulse shortening hinders improvement of microwave output energy for high power microwave tubes. So far, it is also an unresolved problem in the field of high power microwave devices. In this paper, relativistic backward wave tube (RBWO) is treated as an example to study the pulse shortening phenomena. The influences of gas existing in the tube and explosive emission in inner surface of RBWO are all investigated by means of the particle-in-cell method. Through the simulation results, it can be predicted that the background gas in the tube is one but not the most important factor resulting in pulse shortening, in order to broaden the pulse width of gas-filled RBWO, the pressure of the filled gas must be controlled in a proper value. The explosive emission in the surface of slow wave structure due to intense electric field is one of the most important factors causing pulse shortening in high power microwave tube.Some methods to overcome this find of explosive emission are also given.

  17. Pulsed electron beams in transient plasmas

    International Nuclear Information System (INIS)

    In the present work a large variety of experimental investigation is reviewed, having in common pulsed electron beams in transient plasmas. The simulation of nuclear pumping of plasma recombination lasers using pulsed electron beams led to the optimization of a coaxial discharge geometry which allowed lasing at the 585.3 nm transition in Ne I, Ne-H2 mixtures. In a detailed investigation of the cathode sheaths by superposition of two discharges, a simple and accurate method to measure the sheath width has been worked out and a new way of pulsed electron beam generation has been discovered. The electron beam (280 A peak current, 10 ns pulse duration, diameter less than 100 μm over a few centimeters length) is produced in a pseudospark-like discharge without inner diaphragms by the synergy of two discharges. Its parameters can be efficiently controlled by the preionization discharge. The exceptional radial stability of this beam along the discharge tube access opens the possibility to use the device as a pulsed high-density ion trap. The extension of this research helped to discover and to explain the (Cruise) effect, namely the capture and guiding of the electron beam by dielectric fibres. (author) 10 figs., 64 refs

  18. Pulse oximetry in bronchiolitis: is it needed?

    Directory of Open Access Journals (Sweden)

    Hendaus MA

    2015-10-01

    Full Text Available Mohamed A Hendaus,1,2 Fatima A Jomha,3 Ahmed H Alhammadi,1,2 1Department of Pediatrics, General Pediatrics Division, Hamad Medical Corporation, 2Weill-Cornell Medical College, Doha, Qatar; 3School of Pharmacy, Lebanese International University, Khiara, Lebanon Abstract: 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. Keywords: bronchiolitis, children, monitor, oxygen

  19. Thyristor stack for pulsed inductive plasma generation.

    Science.gov (United States)

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

    2009-03-01

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

  20. Pulse Shaping Entangling Gates and Error Supression

    Science.gov (United States)

    Hucul, D.; Hayes, D.; Clark, S. M.; Debnath, S.; Quraishi, Q.; Monroe, C.

    2011-05-01

    Control of spin dependent forces is important for generating entanglement and realizing quantum simulations in trapped ion systems. Here we propose and implement a composite pulse sequence based on the Molmer-Sorenson gate to decrease gate infidelity due to frequency and timing errors. The composite pulse sequence uses an optical frequency comb to drive Raman transitions simultaneously detuned from trapped ion transverse motional red and blue sideband frequencies. The spin dependent force displaces the ions in phase space, and the resulting spin-dependent geometric phase depends on the detuning. Voltage noise on the rf electrodes changes the detuning between the trapped ions' motional frequency and the laser, decreasing the fidelity of the gate. The composite pulse sequence consists of successive pulse trains from counter-propagating frequency combs with phase control of the microwave beatnote of the lasers to passively suppress detuning errors. We present the theory and experimental data with one and two ions where a gate is performed with a composite pulse sequence. This work supported by the U.S. ARO, IARPA, the DARPA OLE program, the MURI program; the NSF PIF Program; the NSF Physics Frontier Center at JQI; the European Commission AQUTE program; and the IC postdoc program administered by the NGA.

  1. Thyristor stack for pulsed inductive plasma generation.

    Science.gov (United States)

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

    2009-03-01

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

  2. Pulsed power supply for Nova Upgrade

    International Nuclear Information System (INIS)

    This report describes work carried out at the Center for Electromechanics at The University of Texas at Austin (CEM-UT). A baseline design of the Nova Upgrade has been completed by Lawrence Livermore National Laboratory. The Nova Upgrade is an 18 beamline Nd: glass laser design utilizing fully relayed 4x4 30 cm aperture segmented optical components. The laser thus consists of 288 independent beamlets nominally producing 1.5 to 2.0 MJ of 0.35 μm light in a 3 to 5 ns pulse. The laser design is extremely flexible and will allow a wide range of pulses to irradiate ICF targets. This facility will demonstrate ignition/gain and the scientific feasibility of ICF for energy and defense applications. The pulsed power requirements for the Nova Upgrade are given. CEM-UT was contracted to study and develop a design for a homopolar generator/inductor (HPG/inductor) opening switch system which would satisfy the pulsed power supply requirements of the Nova Upgrade. The Nd:glass laser amplifiers used in the Nova Upgrade will be powered by light from xenon flashlamps. The pulsed power supply for the Nova Upgrade powers the xenon flashlamps. This design and study was for a power supply to drive flashlamps

  3. Binary rf pulse compression experiment at SLAC

    Energy Technology Data Exchange (ETDEWEB)

    Lavine, T.L.; Spalek, G.; Farkas, Z.D.; Menegat, A.; Miller, R.H.; Nantista, C.; Wilson, P.B.

    1990-06-01

    Using rf pulse compression it will be possible to boost the 50- to 100-MW output expected from high-power microwave tubes operating in the 10- to 20-GHz frequency range, to the 300- to 1000-MW level required by the next generation of high-gradient linacs for linear for linear colliders. A high-power X-band three-stage binary rf pulse compressor has been implemented and operated at the Stanford Linear Accelerator Center (SLAC). In each of three successive stages, the rf pulse-length is compressed by half, and the peak power is approximately doubled. The experimental results presented here have been obtained at low-power (1-kW) and high-power (15-MW) input levels in initial testing with a TWT and a klystron. Rf pulses initially 770 nsec long have been compressed to 60 nsec. Peak power gains of 1.8 per stage, and 5.5 for three stages, have been measured. This corresponds to a peak power compression efficiency of about 90% per stage, or about 70% for three stages, consistent with the individual component losses. The principle of operation of a binary pulse compressor (BPC) is described in detail elsewhere. We recently have implemented and operated at SLAC a high-power (high-vacuum) three-stage X-band BPC. First results from the high-power three-stage BPC experiment are reported here.

  4. The Pulsed Spectra of Two Extraordinary Pulsars

    CERN Document Server

    Roberts, M S E; Ibrahim, A; Kaspi, V M; Markwardt, C B; Ransom, S M; Swank, J H; Woods, P; Gavriil, Fotis; Ibrahim, Alaa; Kaspi, Victoria M.; Markwardt, Craig; Ransom, Scott M.; Roberts, Mallory S.E.; Swank, Jean H.; Woods, Pete

    2004-01-01

    We report on X-ray monitoring of two isolated pulsars within the same RXTE field of view. PSR J1811-1925 in the young supernova remnant G11.2-0.3 has a nearly sinusoidal pulse profile with a hard pulsed spectrum (photon index \\~1.2). The pulsar is a highly efficient (~ 1% of spin-down energy) emitter of 2-50 keV pulsed X-rays despite having a fairly typical B ~ 2e12 G magnetic field. PSR J1809-1943/XTE J1810-197 is a newly discovered slow (P=5.54 s), apparently isolated X-ray pulsar which increased in flux by a factor of ~100 in 2003 January. Nine months of monitoring observations have shown a decrease in pulsed flux of ~ 30% without a significant change in its apparently thermal spectrum (kT ~0.7 keV) or pulse profile. During this time, the spin-down torque has fluctuated by a factor of ~ 2. Both the torque and the flux have remained steady for the last 3 months, at levels consistent with a magnetar interpretation.

  5. Drop deformation by laser-pulse impact

    CERN Document Server

    Gelderblom, Hanneke; Klein, Alexander L; Bouwhuis, Wilco; Lohse, Detlef; Villermaux, Emmanuel; Snoeijer, Jacco H

    2015-01-01

    A free-falling absorbing liquid drop hit by a nanosecond laser-pulse experiences a strong recoil-pressure kick. As a consequence, the drop propels forward and deforms into a thin sheet which eventually fragments. We study how the drop deformation depends on the pulse shape and drop properties. We first derive the velocity field inside the drop on the timescale of the pressure pulse, when the drop is still spherical. This yields the kinetic-energy partition inside the drop, which precisely measures the deformation rate with respect to the propulsion rate, before surface tension comes into play. On the timescale where surface tension is important the drop has evolved into a thin sheet. Its expansion dynamics is described with a slender-slope model, which uses the impulsive energy-partition as an initial condition. Completed with boundary integral simulations, this two-stage model explains the entire drop dynamics and its dependance on the pulse shape: for a given propulsion, a tightly focused pulse results in a...

  6. Control of giant pulse duration in neodymium mini lasers with controllable cavity length and pulsed pumping

    International Nuclear Information System (INIS)

    In a solid-state laser incident on aLiNdP4O12 crystal, pumped by a short light pulse, giant pulse oscillation without the use of resonator Q switching is realized. Tuning of the oscillation pulse duration from 2 up to 20 ns is achieved by changing the cavity length from 24 to 3 mm, respectively. Our analysis of this mode of laser radiation is made on the basis of the rate equations. The factors influencing oscillation pulse duration a reinvestigated. It is shown that in a limiting case the minimal value of the pulse duration is limited by only the rate of excitation transfer from the pumping band to the metastable level

  7. Nonlinear Pulse Shaping in Fibres for Pulse Generation and Optical Processing

    Directory of Open Access Journals (Sweden)

    Sonia Boscolo

    2012-01-01

    Full Text Available The development of new all-optical technologies for data processing and signal manipulation is a field of growing importance with a strong potential for numerous applications in diverse areas of modern science. Nonlinear phenomena occurring in optical fibres have many attractive features and great, but not yet fully explored, potential in signal processing. Here, we review recent progress on the use of fibre nonlinearities for the generation and shaping of optical pulses and on the applications of advanced pulse shapes in all-optical signal processing. Amongst other topics, we will discuss ultrahigh repetition rate pulse sources, the generation of parabolic shaped pulses in active and passive fibres, the generation of pulses with triangular temporal profiles, and coherent supercontinuum sources. The signal processing applications will span optical regeneration, linear distortion compensation, optical decision at the receiver in optical communication systems, spectral and temporal signal doubling, and frequency conversion.

  8. Effect of Pulse Parameters on Weld Quality in Pulsed Gas Metal Arc Welding: A Review

    Science.gov (United States)

    Pal, Kamal; Pal, Surjya K.

    2011-08-01

    The weld quality comprises bead geometry and its microstructure, which influence the mechanical properties of the weld. The coarse-grained weld microstructure, higher heat-affected zone, and lower penetration together with higher reinforcement reduce the weld service life in continuous mode gas metal arc welding (GMAW). Pulsed GMAW (P-GMAW) is an alternative method providing a better way for overcoming these afore mentioned problems. It uses a higher peak current to allow one molten droplet per pulse, and a lower background current to maintain the arc stability. Current pulsing refines the grains in weld fusion zone with increasing depth of penetration due to arc oscillations. Optimum weld joint characteristics can be achieved by controlling the pulse parameters. The process is versatile and easily automated. This brief review illustrates the effect of pulse parameters on weld quality.

  9. Energy distribution of fast electrons accelerated by high intensity laser pulse depending on laser pulse duration

    Science.gov (United States)

    Kojima, Sadaoki; Arikawa, Yasunobu; Morace, Alessio; Hata, Masayasu; Nagatomo, Hideo; Ozaki, Tetsuo; Sakata, Shohei; Lee, Seung Ho; Matsuo, Kazuki; Farley Law, King Fai; Tosaki, Shota; Yogo, Akifumi; Johzaki, Tomoyuki; Sunahara, Atsushi; Sakagami, Hitoshi; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Fujioka, Shinsuke; Azechi, Hiroshi

    2016-05-01

    The dependence of high-energy electron generation on the pulse duration of a high intensity LFEX laser was experimentally investigated. The LFEX laser (λ = 1.054 and intensity = 2.5 – 3 x 1018 W/cm2) pulses were focused on a 1 mm3 gold cubic block after reducing the intensities of the foot pulse and pedestal by using a plasma mirror. The full width at half maximum (FWHM) duration of the intense laser pulse could be set to either 1.2 ps or 4 ps by temporally stacking four beams of the LFEX laser, for which the slope temperature of the high-energy electron distribution was 0.7 MeV and 1.4 MeV, respectively. The slope temperature increment cannot be explained without considering pulse duration effects on fast electron generation.

  10. A Novel Transcranial Magnetic Stimulator Inducing Near Rectangular Pulses with Controllable Pulse Width (cTMS)

    Science.gov (United States)

    Jalinous, Reza; Lisanby, Sarah H.

    2013-01-01

    A novel transcranial magnetic stimulation (TMS) device with controllable pulse width (PW) and near rectangular pulse shape (cTMS) is described. The cTMS device uses an insulated gate bipolar transistor (IGBT) with appropriate snubbers to switch coil currents up to 7 kA, enabling PW control from 5 μs to over 100 μs. The near-rectangular induced electric field pulses use 22–34% less energy and generate 67–72% less coil heating compared to matched conventional cosine pulses. CTMS is used to stimulate rhesus monkey motor cortex in vivo with PWs of 20 to 100 μs, demonstrating the expected decrease of threshold pulse amplitude with increasing PW. The technological solutions used in the cTMS prototype can expand functionality, and reduce power consumption and coil heating in TMS, enhancing its research and therapeutic applications. PMID:18232369

  11. PULSE REFERENCED CONTROL METHOD FOR ENHANCED POWER AMPLIFICATION OF A PULSE MODULATED SIGNAL

    DEFF Research Database (Denmark)

    1998-01-01

    To correct for any source of non-linearity and noise introduced in the power amplification of a pulse modulated signal, a correction unit is applied in-between the pulse modulator and the switching power amplification stage. The correction unit is controlled to have a compensating effect, by...... introducing continuous delays on the individual pulse edges on the basis of error information provided by an error processing block. One preferred embodiment of the invention comprises: a Correction Unit with means to control the delays of the individual pulse edges as a function of a control input signal $i......(v¿e?); a state feedback block A with compensation; a reference shaping block $i(R) to modify the pulsed reference $i(v¿r?) for optimized error estimation; a difference block to generate an error signal and a compensator $i(C) to shape this error. The invention makes it possible to implement practical...

  12. Pulsed laser ablation of GaAs using nano pulse length

    International Nuclear Information System (INIS)

    Ablation using very short pulses has shown a great promise in facilitating the growth of complex multi-element films with stoichiometries matching those of their parent materials. GaAs is an important material in the electronic and opto-electronic industries and due to its compound structure it is an intriguing candidate for pulsed laser deposition. This work investigates the effect of nanosecond laser pulse lengths on the ablation of GaAs in an inert atmosphere. The number of pulses was varied in order to find the optimal condition for nano particles formation in our setup. The deposited structures were studied by grazing incidence small angle X-ray scattering and atomic force microscopy. It is shown that the GaAs nanoparticle sizes and size distributions can be controlled partly by the number of laser pulses applied in their production.

  13. A transcranial magnetic stimulator inducing near-rectangular pulses with controllable pulse width (cTMS).

    Science.gov (United States)

    Peterchev, Angel V; Jalinous, Reza; Lisanby, Sarah H

    2008-01-01

    A novel transcranial magnetic stimulation (TMS) device with controllable pulse width (PW) and near-rectangular pulse shape (cTMS) is described. The cTMS device uses an insulated gate bipolar transistor (IGBT) with appropriate snubbers to switch coil currents up to 6 kA, enabling PW control from 5 micros to over 100 micros. The near-rectangular induced electric field pulses use 2%-34% less energy and generate 67%-72% less coil heating compared to matched conventional cosine pulses. CTMS is used to stimulate rhesus monkey motor cortex in vivo with PWs of 20 to 100 micros, demonstrating the expected decrease of threshold pulse amplitude with increasing PW. The technological solutions used in the cTMS prototype can expand functionality, and reduce power consumption and coil heating in TMS, enhancing its research and therapeutic applications. PMID:18232369

  14. Correlation between pulse-width and peak luminosity of single-pulse long gamma-ray bursts

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    With a sample of 21 single-pulse GRBs with redshift measurement and a sample of 65 single-pulse GRBs with pseudo redshift estimated by the luminosity-spectral lag relation,we show that the peak luminosities of GRB pulses are anti-correlated with pulse width,indicating that longer-pulses tend to be dimmer in the gamma-ray band.The anti-correlation is accessible with an internal shock scenario.

  15. Ultra-Wideband, Short Pulse Electromagnetics 9

    CERN Document Server

    Rachidi, Farhad; Kaelin, Armin; Sabath, Frank; UWB SP 9

    2010-01-01

    Ultra-wideband (UWB), short-pulse (SP) electromagnetics are now being used for an increasingly wide variety of applications, including collision avoidance radar, concealed object detection, and communications. Notable progress in UWB and SP technologies has been achieved by investigations of their theoretical bases and improvements in solid-state manufacturing, computers, and digitizers. UWB radar systems are also being used for mine clearing, oil pipeline inspections, archeology, geology, and electronic effects testing. Ultra-wideband Short-Pulse Electromagnetics 9 presents selected papers of deep technical content and high scientific quality from the UWB-SP9 Conference, which was held from July 21-25, 2008, in Lausanne, Switzerland. The wide-ranging coverage includes contributions on electromagnetic theory, time-domain computational techniques, modeling, antennas, pulsed-power, UWB interactions, radar systems, UWB communications, and broadband systems and components. This book serves as a state-of-the-art r...

  16. High voltage, magnetically switched pulsed power systems

    International Nuclear Information System (INIS)

    The principles of magnetic switching are briefly described. Then the results of experiments on the following substantive topics for magnetic switching are presented: material properties and how they relate to switch performance, risetime limitations, and core insulation. Magnetic switching is then evaluated from a system perspective. An idealized pulse power system with 200 kJ or stored energy and a 40 ns output pulse is examined. The multi-megavolt electrical insulation requirements impose limitations on the switches. The cost of the magnetically switched system exceeds the cost of the conventional superpower generator system by up to 75%. The potential for reliability, reproducibility, and repetitive pulse capability must be evaluated for each application to offset the increased cost

  17. Heat pulse propagation studies in JET

    International Nuclear Information System (INIS)

    Heat pulse propagation (HPP) studies in JET have been carried out using a twelve-channel electron cyclotron emission grating (ECE) polychromator. Emphasis is placed on the behaviour of the heat pulse under strong auxiliary heating. The conventional diffusive model for the data-interpretation has been extended so as to take into account the source- and sink terms in the electron power balance equation. It is concluded that the heat pulse is governed by an 'incremental' heat diffusivity, which is related to the incremental confinement time. Experimental results which were obtained during operation of JET are presented, including values of HPP during ohmic heating and HPP during auxiliary heating. These experimental results are discussed with respect to the incremental heat diffusivity. Finally the results of this work are considered in relation to the study of anomalous transport in tokamaks. (U.K.)

  18. Research on Nanosecond Pulse Corona Discharge Attenuation

    International Nuclear Information System (INIS)

    A line-to-plate reactor was set-up in the experimental study on the application of nanosecond pulsed corona discharge plasma technology in environmental pollution control. Investigation on the attenuation and distortion of the amplitude of the pulse wave front and the discharge image as well as the waveform along the corona wire was conducted. The results show that the wave front decreases sharply during the corona discharge along the corona wire. The higher the amplitude of the applied pulse is, the more the amplitude of the wave front decreased. The wave attenuation responds in a lower corona discharge inversely. To get a higher efficiency of the line-to-plate reactor a sharp attenuation of the corona has to be considered in practical design

  19. Intense pulsed ion beams for fusion applications

    International Nuclear Information System (INIS)

    The subject of this review paper is the field of intense pulsed ion beam generation and the potential application of the beams to fusion research. Considerable progress has been made over the past six years. The ion injectors discussed utilize the introduction of electrons into vacuum acceleration gaps in conjunction with high voltage pulsed power technology to achieve high output current. Power levels from injectors exceeding 1000 MW/cm2 have been obtained for pulse lengths on the order of 10-7 sec. The first part of the paper treats the physics and technology of intense ion beams. The second part is devoted to applications of intense ion beams in fusion research. A number of potential uses in magnetic confinement systems have been proposed

  20. RF synchronized short pulse laser ion source

    Energy Technology Data Exchange (ETDEWEB)

    Fuwa, Yasuhiro, E-mail: fuwa@kyticr.kuicr.kyoto-u.ac.jp; Iwashita, Yoshihisa; Tongu, Hiromu; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Okamura, Masahiro [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Yamazaki, Atsushi [Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603 (Japan)

    2016-02-15

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

  1. Pulse current enhanced electrodialytic soil remediation

    DEFF Research Database (Denmark)

    Sun, Tian R.; Ottosen, Lisbeth M.; Jensen, Pernille E.

    2012-01-01

    extent depending on the pulse frequency. The experiment with the frequency of 16 cycles per day showed the best restoration of equilibrium and lowest energy consumption. The energy consumption per removed heavy metals was lower in pulse current experiments than constant current and increased...... in a dramatic decrease in energy consumption, but this change impeded the acidification process and thus the removal of heavy metals decreased significantly. (C) 2012 Elsevier B.V. All rights reserved.......Energy consumption is an important factor influencing the cost of electrodialytic soil remediation (EDR). It has been indicated that the pulse current (in low frequency range) could decrease the energy consumption during EDR. This work is focused on the comparison of energy saving effect...

  2. Research on Nanosecond Pulse Corona Discharge Attenuation

    Institute of Scientific and Technical Information of China (English)

    HE Zheng-hao; XU Huai-li; BAI Jing; YU Fu-sheng; HU Feng; LI Jin

    2007-01-01

    A line-to-plate reactor was set-up in the experimental study on the application of nanosecond pulsed corona discharge plasma technology in environmental pollution control.Investigation on the attenuation and distortion of the amplitude of the pulse wave front and the discharge image as well as the waveform along the corona wire was conducted.The results show that the wave front decreases sharply during the corona discharge along the corona wire.The higher the amplitude of the applied pulse is,the more the amplitude of the wave front decreased.The wave attenuation responds in a lower corona discharge inversely.To get a higher efficiency of the line-to-plate reactor a sharp attenuation of the corona has to be considered in practical design.

  3. 92 K thermoacoustically driven pulse tube refrigerator

    Institute of Scientific and Technical Information of China (English)

    TANG Ke; CHEN Guobang; JIN Tao; KONG Bo; BAO Rui; QIU Limin; GAN Zhihua

    2004-01-01

    @@ A thermoacoustic prime mover, instead of a mechanical compressor, was firstly proposed in 1990 by Radebaugh and Swift et al. to drive a pulse tube refrigerator [1]. The so-called thermoacoustically driven pulse tube refrigerator (TADPTR) has a number of advantages. First,it is characterized by its long-term stable operation for it has no moving components. Besides, solar energy and waste fuel gas can be adopted as its driving source. Utilization of low-grade energy not only improves its overall thermal efficiency, but also is most attractively applicable to the case which is short of electricity but abundant in heat energy. The potential applications, such as thermoacoustic natural gas liquefier, are under development[2].It burns part of natural gas to drive a pulse tube refrigerator whose cooling capacity is then used to liquefy the rest natural gas.

  4. High reflection mirrors for pulse compression gratings.

    Science.gov (United States)

    Palmier, S; Neauport, J; Baclet, N; Lavastre, E; Dupuy, G

    2009-10-26

    We report an experimental investigation of high reflection mirrors used to fabricate gratings for pulse compression application at the wavelength of 1.053microm. Two kinds of mirrors are studied: the mixed Metal MultiLayer Dielectric (MMLD) mirrors which combine a gold metal layer with some e-beam evaporated dielectric bilayers on the top and the standard e-beam evaporated MultiLayer Dielectric (MLD) mirrors. Various samples were manufactured, damage tested at a pulse duration of 500fs. Damage sites were subsequently observed by means of Nomarski microscopy and white light interferometer microscopy. The comparison of the results evidences that if MMLD design can offer damage performances rather similar to MLD design, it also exhibits lower stresses; being thus an optimal mirror substrate for a pulse compression grating operating under vacuum.

  5. A Self-Biasing Pulsed Depressed Collector

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, Mark A.; Jensen, Aaron; Neilson, Jeff; /SLAC

    2014-05-29

    Depressed collectors have been utilized successfully for many years to improve the electrical efficiency of vacuum electron devices. Increasingly, pulsed, high-peak power accelerator applications are placing a premium on electrical efficiency. As RF systems are responsible for a large percentage of the overall energy usage at accelerator laboratories, methods to improve upon the state-of-the-art in pulsed high-power sources are desired. This paper presents a technique for self-biasing the stages in a multistage depressed collector. With this technique, the energy lost during the rise and fall times of the pulse can be recovered, separate power supplies are not needed, and existing modulators can be retrofitted. Calculations show that significant cost savings can be realized with the implementation of this device in high-power systems. In this paper, the technique is described along with experimental demonstration. (auth)

  6. Drop shaping by laser-pulse impact

    CERN Document Server

    Klein, Alexander L; Visser, Claas Willem; Lhuissier, Henri; Sun, Chao; Snoeijer, Jacco H; Villermaux, Emmanuel; Lohse, Detlef; Gelderblom, Hanneke

    2015-01-01

    We study the hydrodynamic response of a falling drop hit by a laser pulse. Combining high-speed with stroboscopic imaging we report that a millimeter-sized dyed water drop hit by a milli-Joule nanosecond laser-pulse deforms and propels forward at several meters per second, until it eventually fragments. We show that the drop motion results from the recoil momentum imparted at the drop surface by water vaporization. We measure the propulsion speed and the time-deformation law of the drop, complemented by boundary integral simulations. We explain the drop propulsion and shaping in terms of the laser pulse energy and drop surface tension. These findings are crucial for the generation of extreme ultraviolet (EUV) light in lithography machines.

  7. Fully automated system for pulsed NMR measurements

    International Nuclear Information System (INIS)

    A system is described which places many of the complex, tedious operations for pulsed NMR experiments under computer control. It automatically optimizes the experiment parameters of pulse length and phase, and precision, accuracy, and measurement speed are improved. The hardware interface between the computer and the NMR instrument is described. Design features, justification of the choices made between alternative design strategies, and details of the implementation of design goals are presented. Software features common to all the available experiments are discussed. Optimization of pulse lengths and phases is performed via a sequential search technique called Uniplex. Measurements of the spin-lattice and spin-spin relaxation times and of diffusion constants are automatic. Options for expansion of the system are explored along with some of the limitations of the system

  8. Theory of laser catalysis with pulses

    CERN Document Server

    Vardi, A

    2001-01-01

    The possibility of accelerating molecular reactions by lasers has attracted considerable theoretical and experimental interest. A particular example of laser-modified reaction dynamics is laser catalysis, a process in which the tunneling through a potential barrier is enhanced by transient excitation to a bound electronic state. We have performed detailed calculations of pulsed laser catalysis on one- and two-dimensional potentials, as a function of the reactants' collision energy and the laser's central frequency. In agreement with previous CW results, the reactive lineshapes are Fano-type curves, resulting from interference between nonradiative tunneling and the optically assisted pathway. In contrast to the CW process, the power requirements of pulsed laser catalysis are well within the reach of commonly used pulsed laser sources, making an experimental realization possible. The laser catalysis scenario is shown to be equivalent in the ``dressed'' state picture, to resonant tunneling through a double-barri...

  9. Highly polarized components of integrated pulse profiles

    CERN Document Server

    Wang, P F

    2016-01-01

    Highly polarized components of pulse profiles are investigated by analyzing observational data and simulating the emission processes. The highly polarized components appear at the leading or trailing part of a pulse profile, which preferably have a flat spectrum and a flat polarization angle curve compared with the low polarized components. By considering the emission processes and propagation effects, we simulate the distributions of wave modes and fractional linear polarization within the entire pulsar emission beam. We show that the highly polarized components can appear at the leading, central, and/or trailing parts of pulse profiles in the models, depending on pulsar geometry. The depolarization is caused by orthogonal modes or scattering. When a sight line cuts across pulsar emission beam with a small impact angle, the detected highly polarized component will be of the O mode, and have a flat polarization angle curve and/or a flat spectrum as observed. Otherwise, the highly polarized component will be o...

  10. Mathematical modeling of the optimum pulse structure for safe and effective photo epilation using broadband pulsed light.

    Science.gov (United States)

    Ash, Caerwyn; Donne, Kelvin; Daniel, Gwenaelle; Town, Godfrey; Clement, Marc; Valentine, Ronan

    2012-09-06

    The objective of this work is the investigation of intense pulsed light (IPL) photoepilation using Monte Carlo simulation to model the effect of the output dosimetry with millisecond exposure used by typical commercial IPL systems. The temporal pulse shape is an important parameter, which may affect the biological tissue response in terms of efficacy and adverse reactions. This study investigates the effect that IPL pulse structures, namely free discharge, square pulse, close, and spaced pulse stacking, has on hair removal. The relationship between radiant exposure distribution during the IPL pulse and chromophore heating is explored and modeled for hair follicles and the epidermis using a custom Monte Carlo computer simulation. Consistent square pulse and close pulse stacking delivery of radiant exposure across the IPL pulse is shown to generate the most efficient specific heating of the target chromophore, whilst sparing the epidermis, compared to free discharge and pulse stacking pulse delivery. Free discharge systems produced the highest epidermal temperature in the model. This study presents modeled thermal data of a hair follicle in situ, indicating that square pulse IPL technology may be the most efficient and the safest method for photoepilation. The investigation also suggests that the square pulse system design is the most efficient, as energy is not wasted during pulse exposure or lost through interpulse delay times of stacked pulses.

  11. Short-pulse laser materials processing

    International Nuclear Information System (INIS)

    The goal of this project was to develop, through experiments and modeling, a better understanding of the physics issues and machining techniques related to short-pulse laser materials processing. Although we have successfully demonstrated many types of cuts in a wide range of materials, our general short-pulse machining scientific knowledge and our ability to model the complex physical processes involved are limited. During this past year we made good progress in addressing some of these issues, but there remain many unanswered questions. Section 2 begins with a theoretical look at short-pulse laser ablation of material using a 1-D radiation-hydrodynamic code which includes a self-consistent description of laser absorption and reflection from an expanding plasma. In Section 3 we present measurements of scaling relationships, hole drilling progression, electric field and polarization effects, and a detailed look at the interesting structures formed during hole drilling of metals under various conditions. Section 4 describes the consequences of the presence of a prepulse before the main drilling pulse. In Section 5 we take a brief look at the plasma plume: how it can be useful, and how we can avoid it. Finally, Section 6 contains a couple of examples of machining non-metals. The laser system used for practically all the experimental results presented here was a short-pulse laser based on Ti:sapphire, which produced 150-fs pulses (minimum) centered at 825 nm, of energy up to 5 mJ at 1 kHz, or 5 W average power

  12. Frequency independent quenching of pulsed emission

    Energy Technology Data Exchange (ETDEWEB)

    Gajjar, Vishal; Joshi, Bhal Chandra [National Centre for Radio Astrophysics (TIFR), Post Bag 3, Ganeshkhind, Pune 411007 (India); Kramer, Michael; Karuppusamy, Ramesh [Max Planck Institute for Radio Astronomy Auf dem Hugel 69, P.O. Box 20 24, D-53010 Bonn (Germany); Smits, Roy, E-mail: gajjar@ncra.tifr.res.in, E-mail: bcj@ncra.tifr.res.in, E-mail: mkramer@mpifr-bonn.mpg.de, E-mail: ramesh@mpifr-bonn.mpg.de, E-mail: smits@astron.nl [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom)

    2014-12-10

    Simultaneous observations at four different frequencies, 313, 607, 1380, and 4850 MHz, for three pulsars, PSRs B0031–07, B0809+74, and B2319+60, are reported in this paper. Identified null and burst pulses are highly concurrent across more than a decade of frequency. A small fraction of non-concurrent pulses (≤3%) is observed, most of which occur at the transition instances. We report, with very high significance for the first time, the full broadband nature of the nulling phenomenon in these three pulsars. These results suggest that nulling invokes changes on the global magnetospheric scale.

  13. Periodic Advertising Pulsing in a Competitive Market

    OpenAIRE

    Marshall Freimer; Dan Horsky

    2012-01-01

    The question as to the optimality of advertising pulsing has attracted many researchers over the last half-century. In this paper we specify a market share model in which there are two advertising-setting firms as well as a no-purchase option. The framework is that of a first-order Markov process with three states. The objective of both firms is to maximize profits. We are able to demonstrate, for a diminishing returns advertising function, that the optimal advertising strategy is pulsing. Th...

  14. Pulsed field magnets at the US NHMFL

    International Nuclear Information System (INIS)

    The pulsed field facility of the National High Magnetic Field Laboratory (NHMFL) consists of four components. Now available are (1) explosive flux compression, (2) capacitor-driven magnets, and (3) a 20 T superconducting magnet. The fourth component, a 60 T quasi-continuous magnet, has been designed and is scheduled for installation in early 1995. All magnets have He-4 cryostats giving temperatures from room temperature (RT) to 2.2-1.5 K. Dilution refrigerators for the superconducting 20 T magnet and the 50 T pulsed magnet will be installed by early 1994. A wide range of experiments have been completed within the past year. ((orig.))

  15. Laser pulses for coherent xuv Raman excitation

    CERN Document Server

    Greenman, Loren; Whaley, K Birgitta

    2014-01-01

    We combine multi-channel electronic structure theory with quantum optimal control to derive Raman pulse sequences that coherently populate a valence excited state. For a neon atom, Raman target populations of up to 13% are obtained. Superpositions of the ground and valence Raman states with a controllable relative phase are found to be reachable with up to 4.5% population and phase control facilitated by the pump pulse carrier envelope phase. Our results open a route to creating core-hole excitations in molecules and aggregates that locally address specific atoms and represent the first step towards realization of multidimensional spectroscopy in the xuv and x-ray regimes.

  16. Short pulse high power fiber laser systems

    OpenAIRE

    Malinowski, A.; Piper, A; Price, J.H.V.; He, F.; Ibsen, M; Nilsson, J.; Richardson, D J

    2005-01-01

    We review the rapid recent progress in the development of short pulse high-power fiber laser and amplifier devices. Use of cladding pump technology now provides a route to compact and efficient laser and amplifier systems with high beam quality and high output powers. A new Yb-fiber CPA system incorporating a CFBG stretcher with both 2nd and 3rd order dispersion is presented for high pulse energy applications. In addition, a simplified Yb-fiber parabolic amplifier system is also shown to be s...

  17. Strong and superstrong pulsed magnetic fields generation

    CERN Document Server

    Shneerson, German A; Krivosheev, Sergey I

    2014-01-01

    Strong pulsed magnetic fields are important for several fields in physics and engineering, such as power generation and accelerator facilities. Basic aspects of the generation of strong and superstrong pulsed magnetic fields technique are given, including the physics and hydrodynamics of the conductors interacting with the field as well as an account of the significant progress in generation of strong magnetic fields using the magnetic accumulation technique. Results of computer simulations as well as a survey of available field technology are completing the volume.

  18. Classical Dynamics of Free Electromagnetic Laser Pulses

    CERN Document Server

    Goto, S; 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 potential means for experimentally bounding the fundamental length scale in the generalized electrodynamics of Bopp, Lande and Podolsky.

  19. Modeling Pulse Tube Cryocoolers with CFD

    Science.gov (United States)

    Flake, Barrett; Razani, Arsalan

    2004-06-01

    A commercial computational fluid dynamics (CFD) software package is used to model the oscillating flow inside a pulse tube cryocooler. Capabilities for modeling pulse tubes are demonstrated with preliminary case studies and the results presented. The 2D axi-symmetric simulations demonstrate the time varying temperature and velocity fields in the tube along with computation of the heat fluxes at the hot and cold heat exchangers. The only externally imposed boundary conditions are a cyclically moving piston wall at one end of the tube and constant temperature or heat flux boundaries at the external walls of the hot and cold heat exchangers.

  20. Spectral Lag Evolution among -Ray Burst Pulses

    Indian Academy of Sciences (India)

    Lan-Wei Jia; Yun-Feng Liang; En-Wei Liang

    2014-09-01

    We analyse the spectral lag evolution of -ray burst (GRB) pulses with observations by CGRO/BATSE. No universal spectral lag evolution feature and pulse luminosity-lag relation within a GRB is observed.Our results suggest that the spectral lag would be due to radiation physics and dynamics of a given emission episode, possibly due to the longer lasting emission in a lower energy band, and the spectral lag may not be an intrinsic parameter to discriminate the long and short GRBs.

  1. Random Pulse Train Spectrum Calculation Unleashed

    OpenAIRE

    Stepanov, Sander; Venetsanopoulos, Anastasios

    2015-01-01

    For the first time the problem of the full solution for the calculation of the power spectrum density of the random pulse train is solved. This well known problem led to a mistaken publication in the past and even its partial solution was considered worthy of publication in a textbook. The little known solution for only the continues random pulse train spectrum is explained by examples and is extended to cover each signal having a discrete spectrum, too. A developed approach is used to derive...

  2. Pulse Wave Velocity in the Carotid Artery

    DEFF Research Database (Denmark)

    Sørensen, Gertrud Laura; Jensen, Julie Brinck; Udesen, Jesper;

    2008-01-01

    The pulse wave velocity (PWV) in the carotid artery (CA) has been estimated based on ultrasound data collected by the experimental scanner RASMUS at DTU. Data is collected from one test subject using a frame rate (FR) of 4000 Hz. The influence of FRs is also investigated. The PWV is calculated from...... distension wave forms (DWF) estimated using cross-correlation. The obtained velocities give results in the area between 3-4 m/s, and the deviations between estimated PWV from two beats of a pulse are around 10%. The results indicate that the method presented is applicable for detecting the local PWV...

  3. Jittering waves in rings of pulse oscillators.

    Science.gov (United States)

    Klinshov, Vladimir; Shchapin, Dmitry; Yanchuk, Serhiy; Nekorkin, Vladimir

    2016-07-01

    Rings of oscillators with delayed pulse coupling are studied analytically, numerically, and experimentally. The basic regimes observed in such rings are rotating waves with constant interspike intervals and phase lags between the neighbors. We show that these rotating waves may destabilize leading to the so-called jittering waves. For these regimes, the interspike intervals are no more equal but form a periodic sequence in time. Analytic criterion for the emergence of jittering waves is derived and confirmed by the numerical and experimental data. The obtained results contribute to the hypothesis that the multijitter instability is universal in systems with pulse coupling. PMID:27575122

  4. Device for generation of pulsed corona discharge

    Science.gov (United States)

    Gutsol, Alexander F.; Fridman, Alexander; Blank, Kenneth; Korobtsev, Sergey; Shiryaevsky, Valery; Medvedev, Dmitry

    2012-05-08

    The invention is a method and system for the generation of high voltage, pulsed, periodic corona discharges capable of being used in the presence of conductive liquid droplets. The method and system can be used, for example, in different devices for cleaning of gaseous or liquid media using pulsed corona discharge. Specially designed electrodes and an inductor increase the efficiency of the system, permit the plasma chemical oxidation of detrimental impurities, and increase the range of stable discharge operations in the presence of droplets of water or other conductive liquids in the discharge chamber.

  5. Pulse transformer for the AA lithium lens

    CERN Multimedia

    1980-01-01

    The antiprotons emanating from the target were initially focused by a magnetic horn. Later on, a Li-lens was used during operation for the SPS collider, until 1992. A Li-rod (130 mm long, 34 mm in diameter) constituted the secondary of a 1:23 pulse-transformer. The half-sine pulse rose to 1000 kA in 900 microsec. The angular acceptance was 95 mrad. In operation after 1992, for LEAR only, a more modest Li-lens was used (155 mm long, diameter 20 mm, 480 kA, risetime 240 microsec, angular acceptance 75 mrad).

  6. Spectral signature of short attosecond pulse trains

    CERN Document Server

    Mansten, E; Mauritsson, J; Ruchon, T; LHuillier, A; Tate, J; Gaarde, M B; Eckle, P; Guandalini, A; Holler, M; Schapper, F; Gallmann, L; Keller, U

    2008-01-01

    We report experimental measurements of high-order harmonic spectra generated in Ar using a carrier-envelope-offset (CEO) stabilized 12 fs, 800nm laser field and a fraction (less than 10%) of its second harmonic. Additional spectral peaks are observed between the harmonic peaks, which are due to interferences between multiple pulses in the train. The position of these peaks varies with the CEO and their number is directly related to the number of pulses in the train. An analytical model, as well as numerical simulations, support our interpretation.

  7. A pulse generator for xenon lamps

    CERN Document Server

    Janata, E

    2002-01-01

    A pulse generator is described, which enhances the analyzing light emitted from a xenon lamp as used in kinetic photospectrometry experiments. The lamp current is increased to 600 A for a duration of 3 ms; the current is constant within +-0.2% during a time interval of 2 ms. Because of instabilities of the lamp arc during pulsing, the use of the enhanced light source is limited to measuring times up to 500 mu s. The enhancement in light intensity depends on the wavelength and amounts to more than 400-fold in the UV-region.

  8. Spatiotemporal characterization of ultrashort optical vortex pulses

    CERN Document Server

    Miranda, Miguel; Rudawski, Piotr; Guo, Chen; Harth, Anne; L'Huillier, Anne; Arnold, Cord L

    2015-01-01

    Generation of few-cycle optical vortex pulses is challenging due to the large spectral bandwidths, as most vortex generation techniques are designed for monochromatic light. In this work, we use a spiral phase plate to generate few-cycle optical vortices from an ultrafast titanium:sapphire oscillator, and characterize them in the spatiotemporal domain using a recently introduced technique based on spatially resolved Fourier transform spectrometry. The performance of this simple approach to the generation of optical vortices is analyzed from a wavelength dependent perspective, as well as in the spatiotemporal domain, allowing us to completely characterize ultrashort vortex pulses in space, frequency, and time.

  9. Pulse Combustors—Performance and Control

    Institute of Scientific and Technical Information of China (English)

    MichaelZeutzius; ToshiakiSetoguchi; 等

    2000-01-01

    Limited resources of fossil energy require the search for new energy conversion preocesses and the increase of the efficiency of power plants to ensure the energy household in the future,Basically,changing the combustion mode from steady to pulse combustion makes an enormous reduction of fuel consumption possible,Active control systems for pulse combustors installed into the inlet further improve the efficiency and extend the operating range considerably.The control algorithm including fuel rate-air rate-pressure characteristics and control strategies as well are presented.

  10. Birefringence effects of short probe pulses of electromagnetically induced transparency

    Science.gov (United States)

    Parshkov, Oleg M.; Kochetkova, Anastasia E.; Budyak, Victoria V.

    2016-04-01

    The numerical simulation results of radiations evolution in the presence of electromagnetically induced transparency for J=0-->J=1-->J=2 scheme of degenerate quantum transitions are presented. The pulse regime of wave interaction with Doppler broadening spectral lines was investigated. It was indicated that when the control field is linear polarized, the input circular polarized probe pulse breaks up in the medium into pulses with mutually perpendicular linear polarizations. Polarization direction of one of these pulses coincides with the polarization direction of control fields. The distance, which probe pulse passes in the medium to its full separation, decreases, when input probe pulse duration or control field intensity decreases. The input probe pulse intensity variation almost does not influence separation distance and speed of the linear polarized probe pulses in the medium. The effects, described above, may be interpreted as the birefringence effects of electromagnetically induced transparency in the case of short probe pulse.

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

    International Nuclear Information System (INIS)

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

  12. Compensating for inconsistent high power vircator microwave radar pulse sources

    Science.gov (United States)

    McAulay, Alastair D.

    2012-06-01

    We investigate a vircator as an economical high power pulsed microwave source for radar. Because of the inconsistency of spark gaps in the driver and operation of the tube based vircator, the resulting ringing pulse has a different pulse shape each time a pulse is generated. Therefore every time we pulse the source we must remove the effects of the ringing source pulse from the data resulting from that pulse. Scattering from a scene is considered random (white noise) with a superimposed non-white component due to the pulse. We propose a whitening filter to remove the effects of the ringing pulse from the random data. This produces a similar result as spectral factorization in which we first determine the pulse from the power spectrum of the data and then deconvolve the ringing pulse out of the received data. The removal of pulse specific ringing increases range resolution and allows data from sequential pulses from a single vircator or pulses from separate vircators to be combined for joint processing in a synthetic aperture radar.

  13. Enhancement of beam pulse controllability for a single-pulse formation system of a cyclotron

    Energy Technology Data Exchange (ETDEWEB)

    Kurashima, Satoshi, E-mail: kurashima.satoshi@jaea.go.jp; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Okumura, Susumu [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Taguchi, Mitsumasa [Quantum Beam Science Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Fukuda, Mitsuhiro [Research Center for Nuclear Physics, Osaka University, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

    2015-07-15

    The single-pulse formation technique using a beam chopping system consisting of two types of high-voltage beam kickers was improved to enhance the quality and intensity of the single-pulse beam with a pulse interval over 1 μs at the Japan Atomic Energy Agency cyclotron facility. A contamination rate of neighboring beam bunches in the single-pulse beam was reduced to less than 0.1%. Long-term purification of the single pulse beam was guaranteed by the well-controlled magnetic field stabilization system for the cyclotron magnet. Reduction of the multi-turn extraction number for suppressing the neighboring beam bunch contamination was achieved by restriction of a beam phase width and precise optimization of a particle acceleration phase. In addition, the single-pulse beam intensity was increased by a factor of two or more by a combination of two types of beam bunchers using sinusoidal and saw-tooth voltage waveforms. Provision of the high quality intense single-pulse beam contributed to improve the accuracy of experiments for investigation of scintillation light time-profile and for neutron energy measurement by a time-of-flight method.

  14. Optimal pulse fishing policy in stage-structured models with birth pulses

    International Nuclear Information System (INIS)

    In this paper, we propose exploited models with stage structure for the dynamics in a fish population for which periodic birth pulse and pulse fishing occur at different fixed time. Using the stroboscopic map, we obtain an exact cycle of system, and obtain the threshold conditions for its stability. Bifurcation diagrams are constructed with the birth rate (or pulse fishing time or harvesting effort) as the bifurcation parameter, and these are observed to display complex dynamic behaviors, including chaotic bands with period windows, period-doubling, multi-period-halving and incomplete period-doubling bifurcation, pitch-fork and tangent bifurcation, non-unique dynamics (meaning that several attractors or attractor and chaos coexist) and attractor crisis. This suggests that birth pulse and pulse fishing provide a natural period or cyclicity that make the dynamical behaviors more complex. Moreover, we show that the pulse fishing has a strong impact on the persistence of the fish population, on the volume of mature fish stock and on the maximum annual-sustainable yield. An interesting result is obtained that, after the birth pulse, the population can sustain much higher harvesting effort if the mature fish is removed as early as possible

  15. Optimal pulse fishing policy in stage-structured models with birth pulses

    Energy Technology Data Exchange (ETDEWEB)

    Gao Shujing [Department of Applied Mathematics, Guangzhou University, Guangzhou 510405 (China); Department of Applied Mathematics, Dalian University of Technology, Dalian 116024 (China); E-mail: gaosjmath@tom.com; Chen Lansun [Department of Applied Mathematics, Dalian University of Technology, Dalian 116024 (China); E-mail: lschen@mail.math.ac.cn; Sun Lihua [Department of Applied Mathematics, Dalian University of Technology, Dalian 116024 (China)

    2005-09-01

    In this paper, we propose exploited models with stage structure for the dynamics in a fish population for which periodic birth pulse and pulse fishing occur at different fixed time. Using the stroboscopic map, we obtain an exact cycle of system, and obtain the threshold conditions for its stability. Bifurcation diagrams are constructed with the birth rate (or pulse fishing time or harvesting effort) as the bifurcation parameter, and these are observed to display complex dynamic behaviors, including chaotic bands with period windows, period-doubling, multi-period-halving and incomplete period-doubling bifurcation, pitch-fork and tangent bifurcation, non-unique dynamics (meaning that several attractors or attractor and chaos coexist) and attractor crisis. This suggests that birth pulse and pulse fishing provide a natural period or cyclicity that make the dynamical behaviors more complex. Moreover, we show that the pulse fishing has a strong impact on the persistence of the fish population, on the volume of mature fish stock and on the maximum annual-sustainable yield. An interesting result is obtained that, after the birth pulse, the population can sustain much higher harvesting effort if the mature fish is removed as early as possible.

  16. Timing control of an intense picosecond pulse laser to the SPring-8 synchrotron radiation pulses

    Science.gov (United States)

    Tanaka, Yoshihito; Hara, Toru; Kitamura, Hideo; Ishikawa, Tetsuya

    2000-03-01

    We have developed a control system to synchronize intense picosecond laser pulses to the hard x-ray synchrotron radiation (SR) pulses of SPring-8. A regeneratively amplified mode-locked Ti:sapphire laser is synchronized to 40 ps SR pulses by locking the laser to the radio frequency of the ring. The synchronization of the pulses is monitored by detecting both beams simultaneously on a gold photocathode of a streak camera. This method enabled us to make a precise measurement of the time interval between the beams, even if the trigger of the streak camera drifts. Synchronization between the laser and the SR pulses has been achieved with a precision of ±2 ps for some hours. The stable timing control ensures the possibility of making two-photon excitation and pump-probe experiments with time resolution of a few tens of ps (limited by the pulse duration of the SR). We have used this system to show that closing undulator gaps in the storage ring shifts the arrival time of the SR pulses, in accord with expectations for the increased power loss.

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

    International Nuclear Information System (INIS)

    A long-pulse generator TPG700L based on a Tesla transformer and a series pulse forming network (PFN) is constructed to generate intense electron beams for the purpose of high power microwave (HPM) generation. The TPG700L mainly consists of a 12-stage PFN, a built-in Tesla transformer in a pulse forming line, a three-electrode gas switch, a transmission line with a trigger, and a load. The Tesla transformer and the compact PFN are the key technologies for the development of the TPG700L. This generator can output electrical pulses with a width as long as 200 ns at a level of 8 GW and a repetition rate of 50 Hz. When used to drive a relative backward wave oscillator for HPM generation, the electrical pulse width is about 100 ns on a voltage level of 520 kV. Factors affecting the pulse waveform of the TPG700L are also discussed. At present, the TPG700L performs well for long-pulse HPM generation in our laboratory

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

    Science.gov (United States)

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

    2014-06-01

    A long-pulse generator TPG700L based on a Tesla transformer and a series pulse forming network (PFN) is constructed to generate intense electron beams for the purpose of high power microwave (HPM) generation. The TPG700L mainly consists of a 12-stage PFN, a built-in Tesla transformer in a pulse forming line, a three-electrode gas switch, a transmission line with a trigger, and a load. The Tesla transformer and the compact PFN are the key technologies for the development of the TPG700L. This generator can output electrical pulses with a width as long as 200 ns at a level of 8 GW and a repetition rate of 50 Hz. When used to drive a relative backward wave oscillator for HPM generation, the electrical pulse width is about 100 ns on a voltage level of 520 kV. Factors affecting the pulse waveform of the TPG700L are also discussed. At present, the TPG700L performs well for long-pulse HPM generation in our laboratory.

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

    Science.gov (United States)

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

    2010-03-01

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

  20. SBS pulse compression for excimer inertial fusion energy drivers

    International Nuclear Information System (INIS)

    A key requirement for the development of commercial fusion power plants utilizing inertial confinement fusion (ICF) as a source of thermonuclear power is the availability of reliable, efficient laser drivers. These laser drivers must be capable of delivering UV optical pulses having energies of the order of 5MJ to cryogenic deuterium-tritium (D/T) ICF targets. The current requirements for laser ICF target irradiation specify the laser wavelength, λ ca. 250 nm, pulse duration, τp ca. 6 ns, bandwidth, Δλ ca. 0.1 nm, polarization state, etc. Excimer lasers are a leading candidate to fill these demanding ICF driver requirements. However, since excimer lasers are not storage lasers, the excimer laser pulse duration, τpp, is determined primarily by the length of the excitation pulse delivered to the excimer laser amplifier. Pulsed power associated with efficiently generating excimer laser pulses has a time constant, τpp which falls in the range, 30 τpppp. As a consequence, pulse compression is needed to convert the long excimer laser pulses to pulses of duration τp. These main ICF driver pulses require, in addition, longer, lower power precursor pulses delivered to the ICF target before the arrival of the main pulse. Although both linear and non-linear optical (NLO) pulse compression techniques have been developed, computer simulations have shown that a ''chirped,'' self-seeded, stimulated Brillouin scattering (SBS) pulse compressor cell using SF6 at a density, ρ ca. 1 amagat can efficiently compress krypton fluoride (KrF) laser pulses at λ=248 nm. In order to avoid the generation of output pulses substantially shorter than τp, the optical power in the chirped input SBS ''seed'' beams was ramped. Compressed pulse conversion efficiencies of up to 68% were calculated for output pulse durations of τp ca. ns