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Sample records for attosecond electron pulses

  1. Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses

    OpenAIRE

    Calegari, F; Ayuso, D.; A. Trabattoni; L. Belshaw; De Camillis, S.; Anumula, S.; Frassetto, F.; Poletto, L.; Palacios, A.; Decleva, P.; Greenwood, J. B.; Martin, F; Nisoli, M.

    2014-01-01

    In the last decade attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules and solids. Here we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine, and the subsequent detection of ultrafast dynamics on a sub-4.5-fs temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules repr...

  2. Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses

    Science.gov (United States)

    Calegari, F.; Ayuso, D.; Trabattoni, A.; Belshaw, L.; De Camillis, S.; Anumula, S.; Frassetto, F.; Poletto, L.; Palacios, A.; Decleva, P.; Greenwood, J. B.; Martín, F.; Nisoli, M.

    2014-10-01

    In the past decade, attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules, and solids. Here, we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine and the subsequent detection of ultrafast dynamics on a sub-4.5-femtosecond temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules represents a crucial step forward in attosecond science, which is progressively moving toward the investigation of more and more complex systems.

  3. Ramsey method for Auger-electron interference induced by an attosecond twin pulse

    OpenAIRE

    Buth, Christian; Schafer, Kenneth J.

    2010-01-01

    We examine the archetype of an interference experiment for Auger electrons: two electron wave packets are launched by inner-shell ionizing a krypton atom using two attosecond light pulses with a variable time delay. This setting is an attosecond realization of the Ramsey method of separated oscillatory fields. Interference of the two ejected Auger-electron wave packets is predicted, indicating that the coherence between the two pulses is passed to the Auger electrons. For the detection of the...

  4. High harmonic attosecond pulse train amplification in a free electron laser

    International Nuclear Information System (INIS)

    It is shown using three-dimensional simulations that the temporal structure of an attosecond pulse train, such as that generated via high harmonic generation in noble gases, may be retained in a free electron laser amplifier through to saturation using a mode-locked optical klystron configuration. At wavelengths of ∼12 nm, a train of attosecond pulses of widths ∼300 as with peak powers in excess of 1 GW are predicted.

  5. New method for attosecond-terawatt pulse generation in X-ray free electron laser

    International Nuclear Information System (INIS)

    We propose a novel scheme for generating a terawatt-attosecond pulse from X-ray free-electron laser (XFEL), which is perfectly synchronized to the few cycle IR pulse. Our approach utilizes baseline configuration similar to PAL-XFEL, but adds a current enhanced self-amplified emission (ESASE) module inserted between the linac and the undulater that introduces only a few cycle energy and current modulation in the electron beam. Our scheme is compact and easy to implement and does not require a slotted foil, thereby leading to improved longitudinal coherence of the beam. We demonstrate the viability of our scheme with simulations using PAL-XFEL beam parameters. Attosecond science has emerged as an important research area of ultrafast phenomena during the past decade as it provides a direct access to capturing, measuring and controlling the electronic dynamics in atoms, molecules and condensed matters. However, high-energy isolated attosecond pulses required for the most intriguing nonlinear attosecond experiments spectroscopy are still lacking. Therefore, techniques are to be further developed to make a powerful isolated attosecond pulse in the x-ray range (1 keV and higher). Several techniques have been proposed to achieve attosecond pulses in a free electron laser (FEL). In this vein, we demonstrate in simulation a TW-attosecond pulse in FEL. In our scheme, it utilizes a laser-induced energy modulation to generate a few-cycle current modulation and small optical-delays between undulator modules for radiation alignment. In this work, we are able to show that an isolated 280 attosecond FWHM, 1 TW pulse at 1 keV (1.25 nm) photon energy and an 100 attosecond FWHM, 1 TW pulse at 12.4 keV (0.1 mn) can be generated. This scheme is simple and easy to implement and can be adapted to the existing FEL facilities. It is worthwhile to mention that in this scheme there is still a room for higher power even for shorter undulator lengths via tapering of the undulator or high

  6. Generation of subterawatt-attosecond pulses in a soft x-ray free-electron laser

    Science.gov (United States)

    Huang, Senlin; Ding, Yuantao; Huang, Zhirong; Marcus, Gabriel

    2016-08-01

    We propose a novel scheme to generate attosecond soft x rays in a self-seeded free-electron laser (FEL) suitable for enabling attosecond spectroscopic investigations. A time-energy chirped electron bunch with additional sinusoidal energy modulation is adopted to produce a short seed pulse through a self-seeding monochromator. This short seed pulse, together with high electron current spikes and a cascaded delay setup, enables a high-efficiency FEL with a fresh bunch scheme. Simulations show that using the Linac Coherent Light Source (LCLS) parameters, soft x-ray pulses with a FWHM of 260 attoseconds and a peak power of 0.5 TW can be obtained. This scheme also has the feature of providing a stable central wavelength determined by the self-seeding monochromator.

  7. Strong-field ionization inducing multi-electron-hole coherence probed by attosecond pulses

    Science.gov (United States)

    Zhao, Jing; Yuan, Jianmin; Zhao, Zengxiu

    2016-05-01

    Recent advances in attosecond spectroscopy has enabled resolving electron-hole dynamics in real time. The correlated electron-hole dynamics and the resulted coherence are directly related to how fast the ionization is completed. How the laser-induced electron-hole coherence evolves and whether it can be utilized to probe the core dynamics are among the key questions in attosecond physics or even attosecond chemistry. In this work, we propose a new scenario to apply IR-pump-XUV-probe schemes to resolving strong field ionization induced and attosecond pulse driven electron-hole dynamics and coherence in real time. The coherent driving of both the infrared laser and the attosecond pulse correlates the dynamics of the core-hole and the valence-hole which leads to the otherwise forbidden absorption and emission of XUV photon. An analytical model is developed based on the strong-field approximation by taking into account of the essential multielectron configurations. The emission spectra from the core-valence transition and the core-hole recombination are found modulating strongly as functions of the time delay between the two pulses, which provides a unique insight into the instantaneous ionization and the interplay of the multi-electron-hole coherence.

  8. Optical attosecond pulses and tracking the nonlinear response of bound electrons.

    Science.gov (United States)

    Hassan, M Th; Luu, T T; Moulet, A; Raskazovskaya, O; Zhokhov, P; Garg, M; Karpowicz, N; Zheltikov, A M; Pervak, V; Krausz, F; Goulielmakis, E

    2016-02-01

    The time it takes a bound electron to respond to the electromagnetic force of light sets a fundamental speed limit on the dynamic control of matter and electromagnetic signal processing. Time-integrated measurements of the nonlinear refractive index of matter indicate that the nonlinear response of bound electrons to optical fields is not instantaneous; however, a complete spectral characterization of the nonlinear susceptibility tensors--which is essential to deduce the temporal response of a medium to arbitrary driving forces using spectral measurements--has not yet been achieved. With the establishment of attosecond chronoscopy, the impulsive response of positive-energy electrons to electromagnetic fields has been explored through ionization of atoms and solids by an extreme-ultraviolet attosecond pulse or by strong near-infrared fields. However, none of the attosecond studies carried out so far have provided direct access to the nonlinear response of bound electrons. Here we demonstrate that intense optical attosecond pulses synthesized in the visible and nearby spectral ranges allow sub-femtosecond control and metrology of bound-electron dynamics. Vacuum ultraviolet spectra emanating from krypton atoms, exposed to intense waveform-controlled optical attosecond pulses, reveal a finite nonlinear response time of bound electrons of up to 115 attoseconds, which is sensitive to and controllable by the super-octave optical field. Our study could enable new spectroscopies of bound electrons in atomic, molecular or lattice potentials of solids, as well as light-based electronics operating on sub-femtosecond timescales and at petahertz rates. PMID:26842055

  9. 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.

  10. 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.

  11. Strong-field ionization inducing multi-electron-hole coherence probed by attosecond pulses

    CERN Document Server

    Zhao, Jing; Zhao, Zengxiu

    2015-01-01

    We propose a new scenario to apply IR-pump-XUV-probe schemes to resolving strong field ionization induced and attosecond pulse driven electron-hole dynamics and coherence in real time. The coherent driving of both the infrared laser and the attoscond pulse correlates the dynamics of the core-hole and the valence-hole which leads to the otherwise forbidden absorption and emission of XUV photon. An analytical model is developed based on the strong-field approximation by taking into account of the essential multielectron configurations. The emission spectra from the core-valence transition and the core-hole recombination are found modulating strongly as functions of the time delay between the two pulses, which provides a unique insight into the instantaneous ionization and the interplay of the multi-electron-hole coherence.

  12. Electron correlation in two-photon double ionization of helium from attosecond to FEL pulses

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Lee [Los Alamos National Laboratory

    2009-01-01

    We investigate the role of electron correlation in the two-photon double ionization of helium for ultrashort pulses in the extreme ultraviolet (XUV) regime with durations ranging from a hundred attoseconds to a few femtoseconds. We perform time-dependent ab initio calculations for pulses with mean frequencies in the so-called 'sequential' regime ({Dirac_h}{omega} > 54.4 eV). Electron correlation induced by the time correlation between emission events manifests itself in the angular distribution of the ejected electrons, which strongly depends on the energy sharing between them. We show that for ultrashort pulses two-photon double ionization probabilities scale non-uniformly with pulse duration depending on the energy sharing between the electrons. Most interestingly we find evidence for an interference between direct ('nonsequential') and indirect ('sequential') double photoionization with intermediate shake-up states, the strength of which is controlled by the pulse duration. This observation may provide a route towards measuring the pulse duration of x-ray free-electron laser (XFEL) pulses.

  13. Attosecond x-Ray Pulse Generation by Linear Thomson Scattering of Intense Laser Beam with Relativistic Electron

    Institute of Scientific and Technical Information of China (English)

    TIAN You-Wei; YU Wei; LU Pei-Xiang; Vinod Senecha; HE Feng; DENG De-Gang; XU Han

    2006-01-01

    Linear Thomson scattering of a short pulse laser by relativistic electron has been investigated using computer simulations. It is shown that scattering of an intense laser pulse of~33 fs full width at haff maximum, with an electron of γ0 = 10 initial energy, generates an ultrashort, pulsed radiation of 76 attoseconds with a photon wavelength of 2.5 nm in the backward direction. The scattered radiation generated by a highly relativistic electron has superior quality in terms of its pulse width and angular distribution in comparison to the one generated by lower relativistic energy electron.

  14. Attosecond X-ray free electron laser

    Directory of Open Access Journals (Sweden)

    Kim D. E.

    2013-03-01

    Full Text Available For a real, meaningful pump-probe experiment with attosecond temporal resolution, an isolated attosecond pulse is in demand. In this vein we report the generation of an isolated ~ 148 attosecond pulse duration radiation pulse at 0.1 angstrom wavelength using current enhanced self-amplified spontaneous emission free electron laser. We consider the 10-GeV PAL-XFEL e-beam for enhanced self-amplified spontaneous emission (ESASE scheme. In ESASE, X-ray SASE FEL is combined with a femtosecond laser system. An 800 nm wavelength, 5 fs FWHM carrier envelope phase stabilized laser was employed in ESASE scheme.

  15. 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.

  16. Circularly Polarized Attosecond Pulses and Molecular Atto-Magnetism

    CERN Document Server

    Bandrauk, Andre D

    2014-01-01

    Various schemes are presented for the generation of circularly polarized molecular high-order harmonic generation (MHOHG) from molecules. In particular it is shown that combinations of counter-rotating circularly polarized pulses produce the lowest frequency Coriolis forces with the highest frequency recollisions, thus generating new harmonics which are the source of circular polarized attosecond pulses (CPAPs). These can be used to generate circularly polarized electronic currents in molecular media on attosecond time scale. Molecular attosecond currents allow then for the generation of ultrashort magnetic field pulses on the attosecond time scale, new tools for molecular atto-magnetism (MOLAM).

  17. Methods of Attosecond X-Ray Pulse Generation

    International Nuclear Information System (INIS)

    We review several proposals for generation of solitary attosecond pulses using two types of free electron lasers which are envisioned as future light sources for studies of ultra-fast dynamics using soft and hard x-rays

  18. Coherent Electron Scattering Captured by an Attosecond Quantum Stroboscope

    CERN Document Server

    Mauritsson, J; Gustafsson, E; Swoboda, M; Ruchon, T; LHuillier, A; Schafer, K J

    2007-01-01

    The basic properties of atoms, molecules and solids are governed by electron dynamics which take place on extremely short time scales. To measure and control these dynamics therefore requires ultrafast sources of radiation combined with efficient detection techniques. The generation of extreme ultraviolet (XUV) attosecond (1 as = 10-18 s) pulses has, for the first time, made direct measurements of electron dynamics possible. Nevertheless, while various applications of attosecond pulses have been demonstrated experimentally, no one has yet captured or controlled the full three dimensional motion of an electron on an attosecond time scale. Here we demonstrate an attosecond quantum stroboscope capable of guiding and imaging electron motion on a sub-femtosecond (1 fs = 10-15 s) time scale. It is based on a sequence of identical attosecond pulses which are synchronized with a guiding laser field. The pulse to pulse separation in the train is tailored to exactly match an optical cycle of the laser field and the ele...

  19. Applications of Elliptically Polarized, Few-Cycle Attosecond Pulses

    Science.gov (United States)

    Starace, Anthony F.

    2016-05-01

    Use of elliptically-polarized light opens the possibility of investigating effects that are not accessible with linearly-polarized pulses. This talk presents two new physical effects that are predicted for ionization of the helium atom by few-cycle, elliptically polarized attosecond pulses. For double ionization of He by an intense elliptically polarized attosecond pulse, we predict a nonlinear dichroic effect (i.e., the difference of the two-electron angular distributions in the polarization plane for opposite helicities of the ionizing pulse) that is sensitive to the carrier-envelope phase, ellipticity, peak intensity I, and temporal duration of the pulse. For single ionization of He by two oppositely circularly polarized, time-delayed attosecond pulses we predict that the photoelectron momentum distributions in the polarization plane have helical vortex structures that are exquisitely sensitive to the time-delay between the pulses, their relative phase, and their handedness. Both of these effects manifest the ability to control the angular distributions of the ionized electrons by means of the attosecond pulse parameters. Our predictions are obtained numerically by solving the six-dimensional two-electron time-dependent Schrödinger equation for the case of elliptically polarized attosecond pulses. They are interpreted analytically by means of perturbation theory analyses of the two ionization processes. This work is supported in part by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Award No. DE-FG03-96ER14646.

  20. High-energy attosecond nanoplasmonic-based electron gun

    Science.gov (United States)

    Greig, S. R.; Elezzabi, A. Y.

    2016-03-01

    We present the design of an ultrafast conical lens based nanoplasmonic electron gun. Through excitation with a radially polarized laser pulse, and a combination of magnetostatic and spatial filtering, high energy electron packets with attosecond durations can be achieved.

  1. Attosecond imaging.

    Science.gov (United States)

    Vrakking, Marc J J

    2014-02-21

    The natural timescale for electron dynamics reaches down to the attosecond domain. Following the discovery of attosecond laser pulses, about a decade ago, attosecond science has developed into a vibrant, new research field, where the motion of single or multiple electrons and, in molecules, the coupling of electronic and nuclear motion, can be investigated, on attosecond to few-femtosecond timescales. Attosecond experiments require suitable observables. This review describes how "attosecond imaging", basing itself on kinetic energy and angle-resolved detection of photoelectrons and fragment ions using a velocity map imaging (VMI) spectrometer, has been exploited in a number of pump-probe experiments. The use of a VMI spectrometer in attosecond experiments has allowed the characterization of attosecond pulse trains and isolated attosecond pulses, the elucidation of continuum electron dynamics and wave packet interferometry in atomic photoionization and the observation of electron localization in dissociative molecular photoionization. PMID:24398785

  2. Quantum model simulations of attosecond electron diffraction

    Institute of Scientific and Technical Information of China (English)

    Peter; BAUM; Jrn; MANZ; Axel; SCHILD

    2010-01-01

    Ultrafast diffraction with free attosecond electron pulses promises insight into the four-dimensional motion of charge density inatoms,molecules and condensed matter. Here we consider the quantum dynamics of the electron-electron scattering process on anattosecond time scale. By numerically solving the time-dependent two-electron Schrdinger equation,we investigate the interactionof an incoming keV-range electron wavepacket by the bound electron of an aligned H+2 molecule,using a one-dimensional model.Our findings reveal the ratio of elastic to inelastic contributions,the role of exchange interaction,and the influence of the molecularelectron density to diffraction. Momentum transfer during the scattering process,from the incoming to the bound electron mediatedby the nuclei,leaves the bound electron in a state of coherent oscillation with attosecond recurrences. Entanglement causes relatedstate-selective oscillations in the phase shift of the scattered electron. Two scenarios of distinguishable and indistinguishable freeand bound electrons yield equivalent results,irrespective of the electronic spins. This suggests to employ the scenario of distinguishable electrons,which is computationally less demanding. Our findings support the possibility of using electron diffraction forimaging the motion of charge density,but also suggest the application of free electron pulses for inducing attosecond dynamics.

  3. Two-electron time-delay interference in atomic double ionization by attosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Rescigno, Thomas N

    2009-10-04

    A two-color two-photon atomic double ionization experiment using subfemtosecond UV pulses can be designed such that the sequential two-color process dominates and one electron is ejected by each pulse. Nonetheless, ab initio calculations show that, for sufficiently short pulses, a prominent interference pattern in the joint energy distribution of the sequentially ejected electrons can be observed that is due to their indistinguishability and the exchange symmetry of the wave function.

  4. Generating Isolated Terawatt-Attosecond X-ray Pulses via a Chirped Laser Enhanced High-Gain Free-electron Laser

    CERN Document Server

    Wang, Zhen; Zhao, Zhentang

    2016-01-01

    A feasible method is proposed to generate isolated attosecond terawatt x-ray radiation pulses in high-gain free-electron lasers. In the proposed scheme, a frequency chirped laser pulse is employed to generate a gradually-varied spacing current enhancement of the electron beam and a series of spatiotemporal shifters are applied between the undulator sections to amplify a chosen ultra-short radiation pulse from self-amplified spontaneous emission. Three-dimensional start-to-end simulations have been carried out and the calculation results demonstrated that 0.15 nm x-ray pulses with peak power over 1TW and duration of several tens of attoseconds could be achieved by using the proposed technique.

  5. 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.

  6. 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)

  7. Generation of atto-second pulses on relativistic mirror plasma

    International Nuclear Information System (INIS)

    When an ultra intense femtosecond laser (I > 1016 W.cm-2) with high contrast is focused on a solid target, the laser field at focus is high enough to completely ionize the target surface during the rising edge of the laser pulse and form a plasma. This plasma is so dense (the electron density is of the order of hundred times the critical density) that it completely reflects the incident laser beam in the specular direction: this is the so-called 'plasma mirror'. When laser intensity becomes very high, the non-linear response of the plasma mirror to the laser field periodically deforms the incident electric field leading to high harmonic generation in the reflected beam. In the temporal domain this harmonic spectrum is associated to a train of atto-second pulses. The goals of my work were to get a better comprehension of the properties of harmonic beams produced on plasma mirrors and design new methods to control theses properties, notably in order to produce isolated atto-second pulses instead of trains. Initially, we imagined and modeled the first realistic technique to generate isolated atto-second on plasma mirrors. This brand new approach is based on a totally new physical effect: 'the atto-second lighthouse effect'. Its principle consists in sending the atto-second pulses of the train in different directions and selects one of these pulses by putting a slit in the far field. Despite its simplicity, this technique is very general and applies to any high harmonic generation mechanism. Moreover, the atto-second lighthouse effect has many other applications (e.g in metrology). In particular, it paves the way to atto-second pump-probe experiments. Then, we studied the spatial properties of these harmonics, whose control and characterization are crucial if one wants to use this source in future application experiments. For instance, we need to control very precisely the harmonic beam divergence in order to achieve the atto-second lighthouse effect and get isolated

  8. Charge Migration in Phenylalanine Initiated by Attosecond Pulses

    Science.gov (United States)

    Greenwood, Jason; Trabattoni, Andrea; Ayuso, David; Belshaw, Louise; de Camillis, Simone; Anumula, Sunil; Frassetto, Fabio; Poletto, Luca; Palacios, Alicia; Declava, Piero; Martin, Fernando; Calegari, Francesca; Nisoli, Mauro

    2015-05-01

    In the past few years attosecond techniques have been implemented for the investigation of ultrafast dynamics in molecules. The generation of isolated attosecond pulses characterized by a relatively high photon flux has opened up new possibilities in the study of molecular dynamics. We report on experimental and theoretical results of ultrafast charge dynamics in a biochemically relevant molecule, namely, the amino acid phenylalanine. The data represent the first experimental demonstration of the generation and observation of a charge migration process in a complex molecule, where electron dynamics precede nuclear motion. The application of attosecond technology to the investigation of electron dynamics in biologically relevant molecules represents a multidisciplinary work, which can open new research frontiers: those in which few femtosecond and even sub-femtosecond electron processes determine the fate of biomolecules.

  9. Developing a High-Flux Isolated Attosecond Pulse Source

    Science.gov (United States)

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

    2016-05-01

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

  10. Single 100-terawatt attosecond X-ray light pulse generation

    CERN Document Server

    Xu, X R; Zhang, Y X; Lu, H Y; Zhang, H; Dromey, B; Zhu, S P; Zhou, C T; Zepf, M; He, X T

    2016-01-01

    The birth of attosecond light sources is expected to inspire a breakthrough in ultrafast optics, which may extend human real-time measurement and control techniques into atomic-scale electronic dynamics. For applications, it is essential to obtain a single attosecond pulse of high intensity, large photon energy and short duration. Here we show that single 100-terawatt attosecond X-ray light pulse with intensity ${1\\times10^{21}}\\textrm{W}/\\textrm{cm}^{{ 2}}$ and duration ${7.9} \\textrm{as}$ can be produced by intense laser irradiation on a capacitor-nanofoil target composed of two separate nanofoils. In the interaction, a strong electrostatic potential develops between two nanofoils, which drags electrons out of the second foil and piles them up in vacuum, forming an ultradense relativistic electron nanobunch. This nanobunch exists in only half a laser cycle and smears out in others, resulting in coherent synchrotron emission of a single pulse. Such an unprecedentedly giant attosecond X-ray pulse may bring us...

  11. Coherent Electron Scattering Captured by an Attosecond Quantum Stroboscope

    International Nuclear Information System (INIS)

    We demonstrate a quantum stroboscope based on a sequence of identical attosecond pulses that are used to release electrons into a strong infrared (IR) laser field exactly once per laser cycle. The resulting electron momentum distributions are recorded as a function of time delay between the IR laser and the attosecond pulse train using a velocity map imaging spectrometer. Because our train of attosecond pulses creates a train of identical electron wave packets, a single ionization event can be studied stroboscopically. This technique has enabled us to image the coherent electron scattering that takes place when the IR field is sufficiently strong to reverse the initial direction of the electron motion causing it to rescatter from its parent ion

  12. Direct observation of electron dynamics in the attosecond domain.

    Science.gov (United States)

    Föhlisch, A; Feulner, P; Hennies, F; Fink, A; Menzel, D; Sanchez-Portal, D; Echenique, P M; Wurth, W

    2005-07-21

    Dynamical processes are commonly investigated using laser pump-probe experiments, with a pump pulse exciting the system of interest and a second probe pulse tracking its temporal evolution as a function of the delay between the pulses. Because the time resolution attainable in such experiments depends on the temporal definition of the laser pulses, pulse compression to 200 attoseconds (1 as = 10(-18) s) is a promising recent development. These ultrafast pulses have been fully characterized, and used to directly measure light waves and electronic relaxation in free atoms. But attosecond pulses can only be realized in the extreme ultraviolet and X-ray regime; in contrast, the optical laser pulses typically used for experiments on complex systems last several femtoseconds (1 fs = 10(-15) s). Here we monitor the dynamics of ultrafast electron transfer--a process important in photo- and electrochemistry and used in solid-state solar cells, molecular electronics and single-electron devices--on attosecond timescales using core-hole spectroscopy. We push the method, which uses the lifetime of a core electron hole as an internal reference clock for following dynamic processes, into the attosecond regime by focusing on short-lived holes with initial and final states in the same electronic shell. This allows us to show that electron transfer from an adsorbed sulphur atom to a ruthenium surface proceeds in about 320 as. PMID:16034414

  13. Attosecond Hard X-ray Free Electron Laser

    Directory of Open Access Journals (Sweden)

    Sandeep Kumar

    2013-03-01

    Full Text Available In this paper, several schemes of soft X-ray and hard X-ray free electron lasers (XFEL and their progress are reviewed. Self-amplified spontaneous emission (SASE schemes, the high gain harmonic generation (HGHG scheme and various enhancement schemes through seeding and beam manipulations are discussed, especially in view of the generation of attosecond X-ray pulses. Our recent work on the generation of attosecond hard X-ray pulses is also discussed. In our study, the enhanced SASE scheme is utilized, using electron beam parameters of an XFEL under construction at Pohang Accelerator Laboratory (PAL. Laser, chicane and electron beam parameters are optimized to generate an isolated attosecond hard X-ray pulse at 0.1 nm (12.4 keV. The simulations show that the manipulation of electron energy beam profile may lead to the generation of an isolated attosecond hard X-ray of 150 attosecond pulse at 0.1 nm.

  14. Single attosecond pulse generation via continuum wave packet interference

    Science.gov (United States)

    Zhou, Shengpeng; Yang, Yujun; Ding, Dajun

    2016-07-01

    A single attosecond pulse generation via continuum-continuum interference is investigated theoretically by exposing a single-electron atom in a femtosecond laser field with the intensity in over-the-barrier ionization regime. We show that the ground state of the atom is depleted in such intense laser field and the high-order harmonics (HHG) via continuum to continuum coherence are generated. In a few-cycle monochromatic laser field (5 fs/800 nm, 1.2×1016 W cm-2), a single attosecond pulse with duration of 49 as is obtained from the HHG. With a two-color laser field combined by 1200 nm (8 fs/7.5×1015 W cm-2) and 800 nm (5 fs/1.0×1016 W cm-2), a shorter single pulse with duration of 29 as can further be produced by changing the relative carrier envelope phase of two laser pulses as a result of controlling the electronic quantum path in the intense electric field. Our results also show that a short single attosecond pulse can be generated in a wide range of the relative carrier envelope phase of the two laser pulses.

  15. Attosecond photoelectron spectroscopy of electron transport in solids

    International Nuclear Information System (INIS)

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  16. Attosecond photoelectron spectroscopy of electron transport in solids

    Energy Technology Data Exchange (ETDEWEB)

    Magerl, Elisabeth

    2011-03-31

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  17. Electron Interference in Molecular Circular Polarization Attosecond XUV Photoionization

    Directory of Open Access Journals (Sweden)

    Kai-Jun Yuan

    2015-01-01

    Full Text Available Two-center electron interference in molecular attosecond photoionization processes is investigated from numerical solutions of time-dependent Schrödinger equations. Both symmetric H\\(_2^+\\ and nonsymmetric HHe\\(^{2+}\\ one electron diatomic systems are ionized by intense attosecond circularly polarized XUV laser pulses. Photoionization of these molecular ions shows signature of interference with double peaks (minima in molecular attosecond photoelectron energy spectra (MAPES at critical angles \\(\\vartheta_c\\ between the molecular \\(\\textbf{R}\\ axis and the photoelectron momentum \\(\\textbf{p}\\. The interferences are shown to be a function of the symmetry of electronic states and the interference patterns are sensitive to the molecular orientation and pulse polarization. Such sensitivity offers possibility for imaging of molecular structure and orbitals.

  18. Steering continuum electron dynamics by low-energy attosecond streaking

    Science.gov (United States)

    Geng, Ji-Wei; Xiong, Wei-Hao; Xiao, Xiang-Ru; Gong, Qihuang; Peng, Liang-You

    2016-08-01

    A semiclassical model is developed to understand the electronic dynamics in the low-energy attosecond streaking. Under a relatively strong infrared (IR) pulse, the low-energy part of photoelectrons initialized by a single attosecond pulse (SAP) can either rescatter with the ionic core and induce interferences structures in the momentum spectra of the ionized electrons or be recaptured into the Rydberg states. The Coulomb potential plays essential roles in both the electron rescattering and recapturing processes. We find that by changing the time delay between the SAP and the IR pulse, the photoelectrons yield or the population of the Rydberg states can be effectively controlled. The present study demonstrates a fascinating way to steer the electron motion in the continuum.

  19. Generation of an intense single isolated attosecond pulse by use of two-colour waveform control

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Bin; Yu Yongli; Chu Wei; Yao Jinping; Fu Yuxi; Xiong Hui; Xu Han; Cheng Ya; Xu Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, PO Box 800-211, Shanghai 201800 (China)], E-mail: ycheng-45277@hotmail.com, E-mail: zzxu@mail.shcnc.ac.cn

    2009-07-28

    We theoretically demonstrate the generation of an intense single attosecond pulse by superposing a weak sub-harmonic pulse upon a sine-waveform few-cycle driving pulse. By use of a sine-waveform few-cycle pulse instead of its traditionally used cosine waveform counterpart, we show that efficient tunnel ionization for generating electrons which can revisit their parent ion with high kinetic energy can occur only once in the few-cycle laser field, leading to an increase of efficiency by nearly two orders of magnitude in single attosecond pulse generation as compared with the use of a cosine-waveform field.

  20. Gating attosecond pulse train generation using multicolor laser fields

    International Nuclear Information System (INIS)

    The process of high-order harmonic generation leads to the production of a train of attosecond-duration extreme ultraviolet (XUV) pulses, with one pulse emitted per optical half-cycle. For attosecond pump-probe experiments, a single, isolated attosecond pulse is preferable, requiring an almost continuous spectrum. We show experimentally and numerically that the addition of a second laser field, and later a third, at a noncommensurate frequency relative to the driving field can modify the subcycle shape of the electric field, leading to the appearance of additional spectral components between the usual odd harmonics and in some cases a quasicontinuum. We perform a parametric study of the frequency ratio between the two first laser fields, the result of which is in good agreement with theoretical selection rules. We also show numerically that using three laser frequencies from an optical parametric amplifier can achieve a single attosecond pulse from a 24-fs laser pulse.

  1. Attosecond pulse trains as multi-color coherent control

    CERN Document Server

    Hernández, J V

    2009-01-01

    We present a general description of the interaction between multi-color laser pulses and atoms and molecules, focusing on the experimentally relevant example of infrared (IR) pulses overlapped with attosecond pulse trains (APTs). This formulation reveals explicitly and analytically the role of the delay between the IR pulse and APT as a coherent control parameter. Our formulation also shows the nearly equivalent roles of the delay and the carrier-envelope phase in controlling the interference between different multiphoton pathways. We illustrate these points by investigating the single ionization of He and introduce dressed adiabatic hyperspherical potentials to aid the discussion. We confirm the predictions with a full-dimensional, two-electron solution of the time-dependent Schr\\"odinger equation.

  2. Real-Time Probing of Electron Dynamics Using Attosecond Time-Resolved Spectroscopy

    Science.gov (United States)

    Ramasesha, Krupa; Leone, Stephen R.; Neumark, Daniel M.

    2016-05-01

    Attosecond science has paved the way for direct probing of electron dynamics in gases and solids. This review provides an overview of recent attosecond measurements, focusing on the wealth of knowledge obtained by the application of isolated attosecond pulses in studying dynamics in gases and solid-state systems. Attosecond photoelectron and photoion measurements in atoms reveal strong-field tunneling ionization and a delay in the photoemission from different electronic states. These measurements applied to molecules have shed light on ultrafast intramolecular charge migration. Similar approaches are used to understand photoemission processes from core and delocalized electronic states in metal surfaces. Attosecond transient absorption spectroscopy is used to follow the real-time motion of valence electrons and to measure the lifetimes of autoionizing channels in atoms. In solids, it provides the first measurements of bulk electron dynamics, revealing important phenomena such as the timescales governing the switching from an insulator to a metallic state and carrier-carrier interactions.

  3. Tailoring the amplification of attosecond pulse through detuned X-ray FEL undulator.

    Science.gov (United States)

    Kumar, Sandeep; Kang, Heung-Sik; Kim, Dong Eon

    2015-02-01

    We demonstrate that the amplification of attosecond pulse in X-ray free electron laser (FEL) undulator can be tailored. The characteristic of the amplification of an isolated attosecond pulse in the FEL undulator is investigated. An isolated 180 attoseconds full width half maximum (FWHM) pulse at 1.25 nm with a spectral bandwidth of 1% is injected into an undulator. The simulation results show that for a direct seeding of 3MW, the seed is amplified to the peak power of 106 GW (40 μJ, an output pulse-width of 383 attoseconds) in the presence of a detuning at FEL resonance condition in 100-m long undulator. We note that the introduction of detuning leads to the better performance compared to the case without detuning: shorter by 15.5% in a pulse-width and higher by 76.6% in an output power. Tapering yields a higher power (116% increases in the output power compared to the case without detuning) but a longer pulse (15.4% longer in the pulse-width). It was observed that ± Δλ(r)/8 (Δλ(r)/λ(r) ~1%) is the maximum degree of detuning, beyond which the amplification becomes poor: lower in the output power and longer in the pulse duration. The minimum power for a seed pulse needs to be higher than 1 MW for the successful amplification of an attosecond pulse at 1.25 nm. Also, the electron beam energy-spread must be less than 0.1% for a suitable propagation of attosecond pulse along the FEL undulator under this study. PMID:25836141

  4. Nonlinear Fourier transformation spectroscopy of small molecules with intense attosecond pulse train

    International Nuclear Information System (INIS)

    We have developed an attosecond nonlinear molecular spectroscopic method called nonlinear Fourier transformation spectroscopy (NFTS) that uses an intense attosecond pulse train (APT) to induce multiphoton ionization processes. In the NFTS method, in addition to characterization of the temporal profile of attosecond pulses, the nonlinear molecular responses are encoded in the interferometric autocorrelation traces depending on the molecular species, their fragment ions and their kinetic energy distributions. The principle and applicability of the NFTS method are described in this paper along with the numerical simulations. The method is applied to diatomic molecules (N2 , D2 and O2) and polyatomic molecules (CO2, CH4 and SF6). Our results highlight the fact that nonlinear spectroscopic information of molecules in the short wavelength region can be obtained through the irradiation of intense APT by taking advantage of the broad spectral bandwidth of attosecond pulses. The development of the nonlinear spectroscopic method in attoseconds is expected to pave the way to investigate the ultrafast intramolecular electron motion such as ultrafast charge migration and electron correlation. (review article)

  5. Probing attosecond pulse structures by XUV-induced hole dynamics

    CERN Document Server

    You, Jhih-An; Dahlström, Jan Marcus

    2015-01-01

    We investigate a two-photon ionization process in neon by an isolated attosecond pump pulse and two coherent extreme ultraviolet probe fields. The probe fields, tuned to the 2s-2p transition in the residual ion, allow for coherent control of the photoelectron via indirect interactions with the hole. We show that the photoelectron-ion coincidence signal contains an interference pattern that can be used to reconstruct the temporal structure of attosecond pump pulses. Our results are supported by simulations based on time-dependent configuration-interaction singles and lowest-order perturbation theory within second quantization.

  6. Theory of Attosecond Transient Absorption Spectroscopy of Krypton for Overlapping Pump and Probe Pulses

    OpenAIRE

    Pabst, Stefan; Sytcheva, Arina; Moulet, Antoine; Wirth, Adrian; Goulielmakis, Eleftherios; Santra, Robin

    2012-01-01

    We present the first fully ab initio calculations for attosecond transient absorption spectroscopy of atomic krypton with overlapping pump and probe pulses. Within the time-dependent configuration interaction singles (TDCIS) approach, we describe the pump step (strong-field ionization using a near-infrared pulse) as well as the probe step (resonant electron excitation using an extreme- ultraviolet pulse) from first principles. We extent our TDCIS model and account for the spin-orbit splitting...

  7. Attosecond dynamics of electrons in molecules and liquids

    Science.gov (United States)

    Woerner, Hans Jakob

    2016-05-01

    The ultrafast motion of electrons and holes following light-matter interaction is fundamental to a broad range of chemical and biophysical processes. In this lecture, I will discuss two recent experiments carried out in our group that measure the atomic-scale motion of charge with attosecond temporal resolution (1 as = 10-18 s). The first experiment is carried out on isolated, spatially oriented molecules in the gas phase. We advance high-harmonic spectroscopy to resolve spatially and temporally the migration of an electron hole immediately following ionization of iodoacetylene, while simultaneously demonstrating extensive control over the process. A multidimensional approach, based on the measurement of both even and odd harmonic orders, enables us to reconstruct both quantum amplitudes and phases of the electronic states with a resolution of ~ 100 as. We separately reconstruct quasi-field-free and laser-controlled charge migration as a function of the spatial orientation of the molecule and determine the shape of the hole created by ionization. The second experiment is carried out on a free-flowing microjet of liquid water. We use an attosecond pulse train synchronized with a near-infrared laser pulse to temporally resolve the process of photoemission from liquid water using the RABBIT technique. We measure a delay on the order of 50 as between electrons emitted from the HOMO of liquid water compared to that of gas-phase water and a substantially reduced modulation contrast of the corresponding sidebands. Since our measurements on solvated water molecules are referenced to isolated ones, the measured delays reflect (i) the photoionization delays caused by electron transport through the aqueous environment and (ii) the effect of solvation on the parent molecule. The relative modulation contrast, in turn, contains information on (iii) the modification of transition amplitudes and (iv) dephasing processes. These experiments make the liquid phase and its fascinating

  8. Temporal Characterization of individual Harmonics of an attosecond pulse train by THz Streaking

    CERN Document Server

    Ardana-Lamas, F; Stepanov, A; Gorgisyan, I; Juranic, P; Abela, R; Hauri, C P

    2015-01-01

    We report on the global temporal pulse characteristics of individual harmonics in an attosecond pulse train by means of photo-electron streaking in a strong low-frequency transient. The scheme allows direct retrieval of pulse durations and first order chirp of individual harmonics without the need of temporal scanning. The measurements were performed using an intense THz field generated by tilted phase front technique in LiNbO_3 . Pulse properties for harmonics of order 23, 25 and 27 show that the individual pulse durations and linear chirp are decreasing by the harmonic order.

  9. Attosecond pulse characterization with coherent Rydberg wavepackets

    CERN Document Server

    Pabst, Stefan

    2016-01-01

    We propose a new technique to fully characterize the temporal structure of extreme ultraviolet pulses by ionizing a bound coherent electronic wavepacket. The populated energy levels make it possible to interfere different spectral components leading to quantum beats in the photoelectron spectrum as a function of the delay between ionization and initiation of the wavepacket. The influence of the dipole phase, which is the main obstacle for state-of-the-art pulse characterization schemes, can be eliminated by angle integration of the photoelectron spectrum. We show that particularly atomic Rydberg wavepackets are ideal and that wavepackets involving multiple electronic states provide redundant information which can be used to cross-check the consistency of the phase reconstruction.

  10. Investigation of the Newly Proposed Carrier-Envelope-Phase Stable Attosecond Pulse Source

    CERN Document Server

    Tibai, Z; Nagy-Csiha, Zs; Fülöp, J A; Almási, G; Hebling, J

    2016-01-01

    Practical aspects of the robust method we recently proposed for producing few-cycle attosecond pulses with arbitrary waveform in the extreme ultraviolet spectral range are studied numerically. It is based on the undulator radiation of relativistic ultrathin electron layers produced by inverse free-electron laser process. Optimal conditions for nanobunching are given; attosecond pulse energy and waveform, and their stability are studied. For K=0.8 undulator parameter, carrier-envelope-phase stable pulses with >45 nJ energy and 80 as duration at 20 nm, and >250 nJ energy and 240 as duration at 60 nm are predicted with 31 mrad and 13 mrad phase stability, respectively.

  11. High-throughput beamline for attosecond pulses based on toroidal mirrors with microfocusing capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Frassetto, F.; Poletto, L., E-mail: poletto@dei.unipd.it [National Research Council, Institute of Photonics and Nanotechnologies, via Trasea 7, 35131 Padova (Italy); Trabattoni, A.; Anumula, S.; Sansone, G. [Department of Physics, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy); Calegari, F. [National Research Council, Institute of Photonics and Nanotechnologies, Piazza L. da Vinci 32, 20133 Milano (Italy); Nisoli, M. [Department of Physics, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy); National Research Council, Institute of Photonics and Nanotechnologies, Piazza L. da Vinci 32, 20133 Milano (Italy)

    2014-10-15

    We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 10{sup 11} W/cm{sup 2}.

  12. High-throughput beamline for attosecond pulses based on toroidal mirrors with microfocusing capabilities.

    Science.gov (United States)

    Frassetto, F; Trabattoni, A; Anumula, S; Sansone, G; Calegari, F; Nisoli, M; Poletto, L

    2014-10-01

    We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 10(11) W/cm(2).

  13. Attosecond control of collective electron motion in plasmas

    OpenAIRE

    Borot, Antonin; Malvache, Arnaud; Chen, Xiaowei; Jullien, Aurélie; Geindre, Jean-Paul; Audebert, Patrick; Mourou, Gérard; Quéré, Fabien; Lopez-Martens, Rodrigo

    2012-01-01

    Today, light fields of controlled and measured waveform can be used to guide electron motion in atoms and molecules with attosecond precision. Here, we demonstrate attosecond control of collective electron motion in plasmas driven by extreme intensity (≈1018 W cm−2) light fields. Controlled few-cycle near-infrared waves are tightly focused at the interface between vacuum and a solid-density plasma, where they launch and guide subcycle motion of electrons from the plasma with characteristic en...

  14. Klein-Gordon Equation with Casimir Potential for Attosecond Laser Pulse Interaction with Matter

    CERN Document Server

    Kozlovskii, Miroslaw P; Kozlowski, Miroslaw; Marciak-Kozlowska, Janina

    2005-01-01

    In this paper the Klein-Gordon equation (K-GE) is solved for the interaction of attosecond laser pulses with medium in which Casimir force operates. It is shown that for nanoscale structures, NEMS and MEMS, the attosecond laser pulses can be used as the tool for the investigation of the role played by Casimir force on the nanoscale. Key words: Casimir force; NEMS, MEMS, Attosecond laser pulses.

  15. Enhanced multi-colour gating for the generation of high-power isolated attosecond pulses

    OpenAIRE

    Haessler, Stefan; Balčiūnas, T.; Fan, G.; Chipperfield, L.; Baltuska, A.

    2014-01-01

    Isolated attosecond pulses (IAP) generated by high-order harmonic generation are valuable tools that enable dynamics to be studied on the attosecond time scale. The applicability of these IAP would be widened drastically by increasing their energy. Here we analyze the potential of using multi-colour driving pulses for temporally gating the attosecond pulse generation process. We devise how this approach can enable the generation of IAP with the available high-energy kHz-repetition-rate Ytterb...

  16. Harmonic and attosecond pulse enhancement in the presence of noise

    Institute of Scientific and Technical Information of China (English)

    Feng Li-Qiang; Chu Tian-Shu

    2012-01-01

    In this paper,we theoretically investigate the effect of noise on the photoionization,the generation of the high-order harmonic and the attosecond pulse irradiated from a model He+ ion.It shows that by properly adding noise fields,such as Gaussian white noise,random light or colored noise,both the ionization probabilities (IPs) and the harmonic yields can be enhanced by several orders of magnitude.Further,by tuning the noise intensity,a stochastic resonance-like curve is observed,showing the existence of an optimal noise in the ionization enhancement process.Finally,by superposing a properly selected harmonic,an intense attosecond pulse with a duration of 67 as is directly generated.

  17. Attosecond Control of Relativistic Electron Bunches using Two-Colour Fields

    CERN Document Server

    Yeung, M; Bierbach, J; Li, L; Eckner, E; Kuschel, S; Woldegeorgis, A; Rödel, C; Sävert, A; Paulus, G G; Coughlan, M; Dromey, B; Zepf, M

    2016-01-01

    Energy coupling during relativistically intense laser-matter interactions is encoded in the attosecond motion of strongly driven electrons at the pre-formed plasma-vacuum boundary. Studying and controlling this motion can reveal details about the microscopic processes that govern a vast array of light-matter interaction physics and applications. These include research areas right at the forefront of extreme laser-plasma science such as laser-driven ion acceleration1, bright attosecond pulse generation2,3 and efficient energy coupling for the generation and study of warm dense matter4. Here we demonstrate attosecond control over the trajectories of relativistic electron bunches formed during such interactions by studying the emission of extreme ultraviolet (XUV) harmonic radiation. We describe how the precise addition of a second laser beam operating at the second harmonic of the driving laser pulse can significantly transform the interaction by modifying the accelerating potential provided by the fundamental ...

  18. Generation of attosecond soft X-ray pulses in a longitudinal space charge amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Dohlus, M.; Schneidmiller, E.A.; Yurkov, M.V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2011-03-15

    A longitudinal space charge amplifier (LSCA), operating in soft X-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. Broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond X-ray pulses. It is shown that a compact and cheap addition to the soft X-ray free electron laser facility FLASH would allow to generate 60 attosecond (FWHM) long X-ray pulses with the peak power at 100 MW level and a contrast above 98%. (orig.)

  19. Coherent hard x rays from attosecond pulse train-assisted harmonic generation.

    Science.gov (United States)

    Klaiber, Michael; Hatsagortsyan, Karen Z; Müller, Carsten; Keitel, Christoph H

    2008-02-15

    High-order harmonic generation from atomic systems is considered in the crossed fields of a relativistically strong infrared laser and a weak attosecond pulse train of soft x rays. Due to one-photon ionization by the x-ray pulse, the ionized electron obtains a starting momentum that compensates the relativistic drift, which is induced by the laser magnetic field, and allows the electron to efficiently emit harmonic radiation upon recombination with the atomic core in the relativistic regime. This way, short pulses of coherent hard x rays of up to 40 keV energy can be generated. PMID:18278127

  20. The attosecond regime of impulsive stimulated electronic Raman excitation

    CERN Document Server

    Ware, Matthew R; Cryan, James P; Haxton, Daniel J

    2016-01-01

    We have calculated the resonant and nonresonant contributions to attosecond impulsive stimulated electronic Raman scattering (SERS) in regions of autoionizing transitions. Comparison with Multiconfiguration Time-Dependent Hartree-Fock (MCTDHF) calculations find that attosecond SERS is dominated by continuum transitions and not autoionizing resonances. These results agree quantitatively with a rate equation that includes second-order Raman and first-and second-order photoionization rates. Such rate models can be extended to larger molecular systems. Our results indicate that attosecond SERS transition probabilities may be understood in terms of two-photon generalized cross sections even in the high-intensity limit for extreme ultraviolet wavelengths.

  1. Advances in attosecond science

    Science.gov (United States)

    Calegari, Francesca; Sansone, Giuseppe; Stagira, Salvatore; Vozzi, Caterina; Nisoli, Mauro

    2016-03-01

    Attosecond science offers formidable tools for the investigation of electronic processes at the heart of important physical processes in atomic, molecular and solid-state physics. In the last 15 years impressive advances have been obtained from both the experimental and theoretical points of view. Attosecond pulses, in the form of isolated pulses or of trains of pulses, are now routinely available in various laboratories. In this review recent advances in attosecond science are reported and important applications are discussed. After a brief presentation of various techniques that can be employed for the generation and diagnosis of sub-femtosecond pulses, various applications are reported in atomic, molecular and condensed-matter physics.

  2. Single X-Ray Attosecond Pulse Generation by Using Combined Pulses Irradiating on a United Two-Atom System

    Institute of Scientific and Technical Information of China (English)

    CHEN Ji-Gen; LI Chen; CHI Fang-Ping; YANG Yu-Jun

    2007-01-01

    @@ A scheme of a single x-ray attosecond pulse generation from a two-atom system exposed to the combined laser pulses is proposed. Our numerical results show that a single x-ray attosecond pulse rather than a train one can be produced by modulation of ionization.

  3. Coherent hard x-rays from attosecond pulse train-assisted harmonic generation

    OpenAIRE

    Klaiber, Michael; Hatsagortsyan, Karen Z.; Müller, Carsten; Christoph H. Keitel

    2007-01-01

    High-order harmonic generation from atomic systems is considered in the crossed fields of a relativistically strong infrared laser and a weak attosecond-pulse train of soft x-rays. Due to one-photon ionization by the x-ray pulse, the ionized electron obtains a starting momentum that compensates the relativistic drift which is induced by the laser magnetic field, and allows the electron to efficiently emit harmonic radiation upon recombination with the atomic core in the relativistic regime. I...

  4. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    CERN Document Server

    Balogh, Emeric; Dombi, Peter; Fulop, Jozsef A; Farkas, Gyozo; Hebling, Janos; Tosa, Valer; Varju, Katalin; 10.1103/PhysRevA.84.023806

    2011-01-01

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half-cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single atom response yields an attosecond pulse train.

  5. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Balogh, Emeric [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); Kovacs, Katalin [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Dombi, Peter; Farkas, Gyozo [Research Institute for Solid State Physics and Optics, H-1525 Budapest (Hungary); Fulop, Jozsef A.; Hebling, Janos [Department of Experimental Physics, University of Pecs, H-7624 Pecs (Hungary); Tosa, Valer [National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Varju, Katalin [HAS Research Group on Laser Physics, University of Szeged, H-6701 Szeged (Hungary)

    2011-08-15

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  6. A Novel Femtosecond Laser System for Attosecond Pulse Generation

    Directory of Open Access Journals (Sweden)

    Jianqiang Zhu

    2012-01-01

    Full Text Available We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA. The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the KDP crystal as the gain medium to ensure the shortest pulse. After the completion, the laser will deliver about 8 J with pulse duration of about 10 femtoseconds, which should be beneficial to the attosecond pulse generation and other ultrafast experiments.

  7. Attosecond control of orbital parity mix interferences and the relative phase of even and odd harmonics in an attosecond pulse train.

    Science.gov (United States)

    Laurent, G; Cao, W; Li, H; Wang, Z; Ben-Itzhak, I; Cocke, C L

    2012-08-24

    We experimentally demonstrate that atomic orbital parity mix interferences can be temporally controlled on an attosecond time scale. Electron wave packets are formed by ionizing argon gas with a comb of odd and even high-order harmonics, in the presence of a weak infrared field. Consequently, a mix of energy-degenerate even and odd parity states is fed in the continuum by one- and two-photon transitions. These interfere, leading to an asymmetric electron emission along the polarization vector. The direction of the emission can be controlled by varying the time delay between the comb and infrared field pulses. We show that such asymmetric emission provides information on the relative phase of consecutive odd and even order harmonics in the attosecond pulse train. PMID:23002742

  8. Generation of attosecond pulse pair in polar media by chirped few-cycle pulses

    Science.gov (United States)

    Hu, Pidong; Niu, Yueping; Wang, Xiangxin; Gong, Shangqing; Liu, Chengpu

    2016-09-01

    The high-order harmonic generation in a polar medium driven by an initially chirped few-cycle laser pulse is investigated via numerically solving the nonlinear Bloch or Maxwell-Bloch equations based on whether propagation effects are taken into account or not. As a result of the reduction of quantum trajectories number due to the introduction of chirps, an attosecond pulse pair (APP) is generated instead of a general attosecond pulse train. Moreover, the time delay between the two attosecond pulses is tunable. When propagation effects take roles, the peak intensities of the APP can be enhanced at suitable propagation distances without observable duration broadening, and such an enhancement can be modulated by changing medium density.

  9. Comparison of RABITT and FROG measurements in the temporal characterization of attosecond pulse trains

    CERN Document Server

    Kim, Kyung Taec; Park, Mi Na; Imran, Tayyab; Umesh, G; Nam, Chang Hee

    2007-01-01

    The attosecond high harmonic pulses obtained from a long Ar-filled gas cell were characterized by two techniques - the reconstruction of attosecond beating by interference of two-photon transition (RABITT) and frequency-resolved optical gating (FROG) methods. The pulse durations obtained by RABITT and FROG methods agreed within 10 %.

  10. Generation of Attosecond X-Ray Pulse through Coherent Relativistic Nonlinear Thomson Scattering

    CERN Document Server

    Lee, K; Jeong, Y U; Lee, B C; Park, S H

    2005-01-01

    In contrast to some recent experimental results, which state that the Nonlinear Thomson Scattered (NTS) radiation is incoherent, a coherent condition under which the scattered radiation of an incident laser pulse by a bunch of electrons can be coherently superposed has been investigated. The Coherent Relativistic Nonlinear Thomson Scattered (C-RNTS) radiation makes it possible utilizing the ultra-short pulse nature of NTS radiation with a bunch of electrons, such as plasma or electron beams. A numerical simulation shows that a 25 attosecond X-ray pulse can be generated by irradiating an ultra-intense laser pulse of 4x10(19) W/cm2 on an ultra-thin solid target of 50 nm thickness, which is commercially available. The coherent condition can be easily extended to an electron beam from accelerators. Different from the solid target, much narrower electron beam is required for the generation of an attosecond pulse. Instead, this condition could be applied for the generation of intense Compton scattered X-rays with a...

  11. 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.

  12. Optical-induced electrical current in diamond switched by femtosecond–attosecond laser pulses by ab initio simulations

    International Nuclear Information System (INIS)

    The electric current has been switched in diamond by a dual-laser field with an attosecond pulse train and a femtosecond laser, respectively serving to excite and drive electrons. The optical-induced current is simulated by the developed method based on the time-dependent density functional theory. The electric current is induced within several attoseconds with the diamond’s conductivity increased by 16∼23 orders of magnitude. Our work opens the way to extending electronic signal processing from the present gigahertz domain into the exahertz domain. (paper)

  13. State-of-the-art attosecond metrology

    Energy Technology Data Exchange (ETDEWEB)

    Schultze, M., E-mail: martin.schultze@mpq.mpg.de [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Wirth, A.; Grguras, I.; Uiberacker, M.; Uphues, T.; Verhoef, A.J.; Gagnon, J. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Hofstetter, M.; Kleineberg, U. [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Goulielmakis, E. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Krausz, F. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany)

    2011-04-15

    Research highlights: {yields} We present a complete setup for investigations with attosecond temporal resoultion. {yields} Few-cycle visible laser pulses are used to generate xray pulses approaching the atomic unit of time. {yields} Attosecond XUV pulses explore ultrafast electronic dynamics in atoms. - Abstract: Tracking and controlling electron dynamics in the interior of atoms, molecules as well as in solids is at the forefront of modern ultrafast science . Time-resolved studies of these dynamics require attosecond temporal resolution that is provided by an ensemble of techniques consolidated under the term 'attosecond metrology'. This work reports the development and commissioning of what we refer to as next-generation attosecond beamline technology: the AS-1 attosecond beamline at the Max-Planck Institute of Quantum Optics. It consists of a phase-stabilized few-cycle laser system, for the generation of XUV radiation, and modules tailored for the spectral filtering and isolation of attosecond pulses as well as for their temporal characterization. The setup produces the shortest attosecond pulses demonstrated to date and combines them with advanced spectroscopic instrumentation (electron-, ion- and XUV-spectrometers). These pulses serve as temporally confined trigger events (attosecond streaking and tunneling spectroscopy) or probe pulses (attosecond absorption and photoelectron spectroscopy) enabling attosecond chronoscopy to be applied to a broad range of systems belonging to the microcosm.

  14. 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.

  15. Two attosecond pulse transient absorption spectroscopy and extraction of the instantaneous AC Stark shift in helium

    Science.gov (United States)

    Bækhøj, Jens E.; Bojer Madsen, Lars

    2016-07-01

    In two attosecond pulse absorption spectroscopy (TAPAS) the use of two attosecond XUV pulses allows the extraction of atomic and molecular quantum mechanical dipole phases from spectroscopic measurements. TAPAS relies on interference between processes that individually only include a single XUV photon, and therefore does not rely on high intensity attosecond pulses. To show the usefulness and limitations of the TAPAS method we investigate its capability of capturing the instantaneous AC Stark shift induced by a midinfrared 3200 nm pulse in the | 1{{s}}2{{p}}> state of helium.

  16. Genetic optimization of attosecond pulse generation in light-field synthesizers

    CERN Document Server

    Balogh, E; Tosa, V; Goulielmakis, E; Varjú, K; Dombi, P

    2014-01-01

    We demonstrate control over attosecond pulse generation and shaping by numerically optimizing the synthesis of few-cycle to sub-cycle driver waveforms. The optical waveform synthesis takes place in an ultrabroad spectral band covering the ultraviolet-infrared domain. These optimized driver waves are used for ultrashort single and double attosecond pulse production (with tunable separation) revealing the potentials of the light wave synthesizer device demonstrated by Wirth et al. [Science 334, 195 (2011)]. The results are also analyzed with respect to attosecond pulse propagation phenomena.

  17. Effects of pressure and gas-jet thickness on the generation of attosecond pulse

    International Nuclear Information System (INIS)

    We investigate how the intensity and duration of an attosecond pulse generated from high-order harmonic generation are affected by the pressure and thickness of the gas jet by taking into account the macroscopic propagation of both fundamental and harmonic fields. Our simulations show that, limited by the propagation effects, especially the absorption of harmonics, the intensity of an attosecond pulse cannot be improved by just independently increasing the gas pressure or the medium length. On the other hand, due to good phase-matching conditions, the duration of a generated attosecond pulse can be improved by changing the gas pressure. (atomic and molecular physics)

  18. Phase Determination Method to Directly Measure Intensity and Frequency of Temporal Profiles of Attosecond EUV Pulses

    Institute of Scientific and Technical Information of China (English)

    GE Yu-Cheng

    2005-01-01

    @@ A new method of phase determination is presented to directly measure the intensity and frequency temporalprofiles of attosecond EUV pulses. The profiles can be reconstructed from the photoelectron energy spectra measured with two different laser intensities at 0° and 180° with respect to the linear laser polarization using a cross correlation between the femtosecond laser and the attosecond EUV. The method has a temporal measurement range from a quarter to about half of a laser oscillation period. The time resolution depends on the jitter and control precision of laser and EUV pulses. This method improves the time resolution in measuring attosecond EUV pulses.

  19. Coherence revival during the attosecond electronic and nuclear quantum photodynamics of the ozone molecule

    CERN Document Server

    Halász, Gábor J; Lasorne, Benjamin; Robb, Mike A; Gatti, Fabien; Vibók, Ágnes

    2013-01-01

    A coherent superposition of two electronic states of ozone (ground and Hartley B) is prepared with a UV pump pulse. Using the multiconfiguration time-dependent Hartree approach, we calculate the subsequent time evolution of the two corresponding nuclear wave packets and the coherence between them. The resulting wave packet shows an oscillation between the two chemical bonds. Even more interesting, the coherence between the two electronics states reappears after the laser pulse is switched off, which could be observed experimentally with an attosecond probe pulse.

  20. Attosecond gamma-ray pulses via nonlinear Compton scattering in the radiation dominated regime

    CERN Document Server

    Li, Jian-Xing; Galow, Benjamin J; Keitel, Christoph H

    2015-01-01

    The interaction of a relativistic electron bunch with a counter-propagating tightly-focused laser beam is investigated for intensities when the dynamics is strongly affected by its own radiation. The Compton scattering spectra of gamma-radiation are evaluated employing a semiclassical description for the laser-driven electron dynamics and a quantum electrodynamical description for the photon emissions. We show for laser facilities under construction that gamma-ray bursts of few hundred attoseconds and dozens of megaelectronvolt photon energies may be detected in the near-backwards direction of the initial electron motion. Tight focussing of the laser beam and radiation reaction are demonstrated to be jointly responsible for such short gamma-ray bursts which are independent of both duration of electron bunch and laser pulse. Furthermore, the stochastic nature of the gamma-photon emission features signatures in the resulting gamma-ray comb in the case of the application of a multi-cycle laser pulse.

  1. Transient absorption lineshapes in a dense, laser-dressed Helium target probed by attosecond pulse trains

    Science.gov (United States)

    Liao, Chen-Ting; Timmers, Henry; Sandhu, Arvinder

    2014-05-01

    Attosecond transient absorption is an emerging time-resolved spectroscopic technique to explore electron dynamics in atoms and molecules. In this experimental study, we used extreme ultraviolet (XUV) attosecond pulse trains (APTs) in energy range of 20-25 eV to probe the transient excited-state absorption of an optically thick Helium gas sample under the influence of moderately strong (1-3 TW/cm2) , infrared (IR), femtosecond pump pulse. We found that the resonant absorption lineshapes for Helium 1s2p, 1snp, and continuum states show rich dynamics, evolving between Lorenzian and Fano profiles with phases imposed by IR laser pulse and multi-channel quantum-path interference. Both AC Stark shifts and light-induced states were studied as a function of pump-probe delay and IR intensity. By changing the Helium gas density, we observed the lineshape modification due to the macroscopic propagation effects, which is usually not included in the single-atom response model. We found that the 13th and 15th high harmonics of XUV produce two coupled polarizations, and the relative coherence between these two polarizations changes the absorption even when the IR pulse arrives after a long time (about 500 fs) after the XUV. This work is supported by NSF Grant No. PHY-0955274.

  2. Tracing attosecond electron motion inside a molecule by interferences from photoelectron emission

    Energy Technology Data Exchange (ETDEWEB)

    Xu Minghui; Peng Liangyou; Zhang Zheng; Gong Qihuang, E-mail: liangyou.peng@pku.edu.cn, E-mail: qhgong@pku.edu.cn [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China)

    2011-01-28

    We present a theoretical study of photoelectron emission of a homonuclear molecule by an attosecond xuv pulse, which can be regarded as a natural double-slit experiment. We show that attosecond electron motion inside the molecule opens one to two 'slits' for photoionization. Interference fringes in the angle-resolved photoelectron momentum distributions exhibit varying visibility (V), depending on the degree of which-path information (P). The complementarity relation, P{sup 2} + V{sup 2} {<=} 1, is verified in the time-dependent molecule double-slit experiment. Hence, the electron motion can be easily mapped out by measuring the interference visibility. This opens up the prospect of employing interferometric techniques to probe ultrafast intramolecular electronic motions. (fast track communication)

  3. Enhanced multi-colour gating for the generation of high-power isolated attosecond pulses

    CERN Document Server

    Haessler, Stefan; Fan, Guangyu; Chipperfield, Luke E; Baltuška, Andrius

    2014-01-01

    Isolated attosecond pulses (IAP) generated by high-order harmonic generation are valuable tools that enable dynamics to be studied on the attosecond time scale. The applicability of these IAP would be widened drastically by increasing their energy. Here we analyze the potential of using multi-colour driving pulses for temporally gating the attosecond pulse generation process. We devise how this approach can enable the generation of IAP with the available high-energy kHz-repetition-rate Ytterbium-based laser amplifiers (delivering 180-fs, 1030-nm pulses). We show theoretically that this requires a three-colour field composed of the fundamental and its second harmonic as well as a lower-frequency auxiliary component. We present pulse characterization measurements of such auxiliary pulses generated directly by white-light seeded OPA with the required significantly shorter pulse duration than the that of the fundamental. This, combined with our recent experimental results on three-colour waveform synthesis [Phys....

  4. Control of the polarization of attosecond pulses using a two-color field

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz, Camilo; Hoffmann, David J; Torres, Ricardo; Chipperfield, Luke E; Marangos, Jonathan P [Blackett Laboratory, Imperial College London, London SW7 2BW (United Kingdom)], E-mail: camilo@usal.es

    2009-11-15

    Control over the polarization of an attosecond pulse train (APT) is demonstrated theoretically using orthogonally polarized two-color fields. The carrier envelope phase of the two pulses is used as a control parameter to generate both an APT with linear polarization in two nearly perpendicular planes or a train of elliptically polarized pulses of alternating helicity. By using few-cycle driving laser fields an isolated attosecond pulse with elliptical polarization is shown to be generated after selecting the cut-off region of the harmonic spectrum. The control mechanism is explained in terms of classical trajectories.

  5. Monitoring Nonadiabatic Electron-Nuclear Dynamics in Molecules by Attosecond Streaking of Photoelectrons

    Science.gov (United States)

    Kowalewski, Markus; Bennett, Kochise; Rouxel, Jérémy R.; Mukamel, Shaul

    2016-07-01

    Streaking of photoelectrons has long been used for the temporal characterization of attosecond extreme ultraviolet pulses. When the time-resolved photoelectrons originate from a coherent superposition of electronic states, they carry additional phase information, which can be retrieved by the streaking technique. In this contribution we extend the streaking formalism to include coupled electron and nuclear dynamics in molecules as well as initial coherences. We demonstrate how streaked photoelectrons offer a novel tool for monitoring nonadiabatic dynamics as it occurs in the vicinity of conical intersections and avoided crossings. Streaking can provide high time resolution direct signatures of electronic coherences, which affect many primary photochemical and biological events.

  6. Monitoring Nonadiabatic Electron-Nuclear Dynamics in Molecules by Attosecond Streaking of Photoelectrons

    CERN Document Server

    Kowalewski, Markus; Rouxel, Jérémy R; Mukamel, Shaul

    2016-01-01

    Streaking of photoelectrons has long been used for the temporal characterization of attosecond extreme ultraviolet pulses. When the time-resolved photoelectrons originate from a coherent superposition of electronic states, they carry an additional phase information, which can be retrieved by the streaking technique. In this contribution we extend the streaking formalism to include coupled electron and nuclear dynamics in molecules as well as initial coherences and demonstrate how it offers a novel tool to monitor non-adiabatic dynamics as it occurs in the vicinity of conical intersections and avoided crossings. Streaking can enhance the time resolution and provide direct signatures of electronic coherences, which affect many primary photochemical and biological events.

  7. A bright attosecond x-ray pulse train generation in a double-laser-driven cone target

    Science.gov (United States)

    Hu, Li-Xiang; Yu, Tong-Pu; Shao, Fu-Qiu; Luo, Wen; Yin, Yan

    2016-06-01

    By using full three-dimensional particle-in-cell and Monte Carlo simulations, we investigate the generation of a high-brightness attosecond x-ray pulse train in a double-laser-driven cone target. The scheme makes use of two lasers: the first high-intensity laser with a laser peak intensity 1.37 × 1020 W/cm2 irradiates the cone and produces overdense attosecond electron bunches; the second counterpropagating weakly relativistic laser with a laser peak intensity 4.932 × 1017 W/cm2 interacts with the produced electron bunches and a bright x-ray pulse train is generated by Thomson backscattering of the second laser off the attosecond electron bunches. It is shown that the photon flux rises by 5 times using the cone target as compared with a normal channel. Meanwhile, the x-ray peak brightness increases significantly from 1.4 × 1021/(s mm2 mrad2 0.1 keV) to 6.0 × 1021/(s mm2 mrad2 0.1 keV), which is much higher than that of the Thomson x-ray source generated from traditional accelerators. We also discuss the influence of the laser and target parameters on the x-ray pulse properties. This compact bright x-ray source may have diverse applications, e.g., the study of electric dynamics and harmonics emission in the atomic scale.

  8. Optical vortices discern attosecond time delay in electron emission from magnetic sublevels

    CERN Document Server

    Wätzel, Jonas

    2016-01-01

    Photoionization from energetically distinct electronic states may have a relative time delay of tens of attoseconds. Here we demonstrate that pulses of optical vortices allow measuring such attoseconds delays from magnetic sublevels, even from a spherically symmetric target. The di?erence in the time delay is substantial and exhibits a strong angular dependence. Furthermore, we find an atomic scale variation in the time delays depending on the target orbital position in the laser spot. The findings o?er thus a qualitatively new way for a spatio-temporal sensing of the magnetic states from which the photoelectrons originate, with a spatial resolution way below the di?raction limit of the vortex beam. Our conclusions follow from analytical considerations based on symmetry, complemented and confirmed with full numerical simulations of the quantum dynamics.

  9. Technique for the Generation of Attosecond X-Ray Pulses Using an FEL

    International Nuclear Information System (INIS)

    We describe a technique for the generation of an isolated burst of X-ray radiation with a duration of ∼ 100 attoseconds in a free electron laser (FEL) employing self-amplified spontaneous emission. Our scheme relies on an initial interaction of the electron beam with an ultra-short laser pulse in a one-period wiggler followed by compression in a dispersive section. The result of this interaction is to create a sub-femtosecond slice of the electron beam with enhanced growth rates for FEL amplification. After many gain lengths through the FEL undulator, the X-ray output from this slice dominates the radiation of the entire bunch. We consider the impact of various effects on the efficiency of this technique. Different configurations are considered in order to realize various timing structures for the resulting radiation

  10. Control of Attosecond Electron Diffraction by Elliptical Long-Wavelength Radiation

    Science.gov (United States)

    Ranitovic, Predrag; Tong, Xiao-Min; Hickstein, Daniel; Murnane, Margaret; Kapteyn, Henry

    2015-05-01

    Generation of intense laser pulses in the mid-IR regime, has opened door for several novel applications in the ultrafast AMO physics. Attosecond electron diffraction and holography, driven by the mid-IR radiation is one example of these new developments. In this work we utilize a broad range of laser wavelengths (267 to 2000 nm) in a strong-field regime, to obtain holographic 2D images of electrons diffracting off small atoms and molecules. By comparing 2D electron momenta taken with different laser wavelengths, using a VMI geometry, we found that for the long-wavelength laser pulses (1.3 and 2 μm), the main features in the electron momenta come from the interference of the plane, and spherical electron wave packets diffracting off the parent ion. By controlling the ellipticity of the driving laser fields, we were able to tune the returning electron direction, and in turn the amplitudes of the diffracting spherical electron wave packets that carry the information of the electron-ion differential cross sections. In this combined theoretical and experimental work we showed how to control the amplitudes and the phases of these rescattering electron wave packets, and how to use this method to image matter with attosecond temporal and Angstrom spatial resolution.

  11. Attosecond pulse production using resonantly-enhanced high-order harmonics

    CERN Document Server

    Strelkov, V V

    2016-01-01

    We study theoretically the effect of the giant resonance in Xe on the phase difference between the consecutive high order resonantly-enhanced harmonics and calculate the duration of the attosecond pulses produced by these harmonics. For certain conditions resonantly-induced dephasing compensates the phase difference which is intrinsic for the off-resonance harmonics. We find these conditions analytically and compare them with the numerical results. This harmonic synchronization allows attosecond pulse shortening in conjunction with the resonance-induced intensity increase by more than an order of magnitude; the latter enhancement relaxes the requirements for the UV filtering needed for the attosecond pulse production. Using a two-color driving field allows further increase of the intensity. In particular, a caustic-like feature in the harmonic spectrum leads to the generation efficiency growth up to two orders of magnitude, however accompanied by an elongation of the XUV pulse.

  12. Spectral phase measurement of a Fano resonance using tunable attosecond pulses

    Science.gov (United States)

    Kotur, M.; Guénot, D.; Jiménez-Galán, Á.; Kroon, D.; Larsen, E. W.; Louisy, M.; Bengtsson, S.; Miranda, M.; Mauritsson, J.; Arnold, C. L.; Canton, S. E.; Gisselbrecht, M.; Carette, T.; Dahlström, J. M.; Lindroth, E.; Maquet, A.; Argenti, L.; Martín, F.; L'Huillier, A.

    2016-02-01

    Electron dynamics induced by resonant absorption of light is of fundamental importance in nature and has been the subject of countless studies in many scientific areas. Above the ionization threshold of atomic or molecular systems, the presence of discrete states leads to autoionization, which is an interference between two quantum paths: direct ionization and excitation of the discrete state coupled to the continuum. Traditionally studied with synchrotron radiation, the probability for autoionization exhibits a universal Fano intensity profile as a function of excitation energy. However, without additional phase information, the full temporal dynamics cannot be recovered. Here we use tunable attosecond pulses combined with weak infrared radiation in an interferometric setup to measure not only the intensity but also the phase variation of the photoionization amplitude across an autoionization resonance in argon. The phase variation can be used as a fingerprint of the interactions between the discrete state and the ionization continua, indicating a new route towards monitoring electron correlations in time.

  13. Broadband multilayer soft X-ray mirrors for attosecond pulse formation at photon energies above 100 eV

    Energy Technology Data Exchange (ETDEWEB)

    Hofstetter, Michael; Schuster, Joerg; Kleineberg, Ulf [LMU, Physik (Germany); Aquila, Andrew [CXRO (United States); Schulze, Martin; Fiess, Markus; Gouliemakis, Eleftherios; Krausz, Ferenc [MPQ (Germany); Huth, Martin [LMU, Chemie (Germany)

    2009-07-01

    We report on the development, fabrication and application of multilayer mirrors as broadband soft-X-ray optical components for the formation of attosecond (1 asec=10{sup -18}s)pulses from high harmonic radiation. Until recently, attosecond physics was merely confined to the photon energy range below 100 eV due to the properties of Mo/Si multilayer and single isolated pulses of 80 asec pulse duration have been achieved. For many applications, e.g. in the characterization of the photoemission dynamics from solid surfaces or the characterization of ultrafast surface plasmon dynamics in metallic nanostructures by attosecond pump-probe spectroscopy, higher photon energies are desirable to address deeper bound electronic core states or to increase the kinetic energy of the emitted photoelectrons. Here, we introduce new aperiodic broad bandwidth multilayer systems based on lanthanum (e.g. LaMo, LaB{sub 4}CMo, LaB{sub 4}C, MoB{sub 4}C),for the 100-190 eV photon energy range. Multilayer properties like interface roughness, interlayer formation and reflectivity are discussed. Finally, first applications for spectral filtering of the HHG comb above 100 eV are presented.

  14. Quantum path control using attosecond pulse trains via UV-assisted resonance enhance ionization

    Institute of Scientific and Technical Information of China (English)

    李芳; 魏来; 何志聪

    2015-01-01

    We theoretically investigate the quantum path selection in an ultraviolet (UV)-assisted near-infrared field with an UV energy below the ionization threshold. By calculating the ionization probability with different assistant UV frequencies, we find that a resonance-enhanced ionization peak emerges in the region Euvattosecond pulse train (APT) centered in the resonance region, we show that the short quantum path can be well selected in the continuum case. By performing the electron trajectory analysis, we have further explained the physical mechanism of the quantum path selection. Moreover, we also demonstrate that in the resonance region, the harmonic emission from the selected paths is more efficient than that with the APT energy above the ionization threshold.

  15. Attosecond Steering of Electrons with Optimised Strong Field Waveforms

    CERN Document Server

    Haessler, S; Fan, G; Witting, T; Squibb, R; Chipperfield, L; Zaïr, A; Andriukaitis, G; Pugžlys, A; Tisch, J W G; Marangos, J P; Baltuška, A

    2013-01-01

    Quasi-free field driven electron trajectories are a key element of strong-field dynamics. Upon recollision with the parent ion, the energy transferred from the field to the electron may be released as attosecond duration XUV emission1,2 in the process of high harmonic generation (HHG). The conventional sinusoidal driver fields set limitations on the maximum value of this energy transfer, and it has been predicted that this limit can be significantly exceeded by an appropriately ramped-up cycle-shape3.Here, we present an experimental realization of such cycle-shaped waveforms and demonstrate control of the HHG process on the single-atom quantum level via attosecond steering of the electron trajectories. With our optimized optical cycles, we boost the field-ionization launching the electron trajectories, increase the subsequent field-to-electron energy transfer, and reduce the trajectory duration, to obtain greatly enhanced HHG efficiency as well as spectral extension compared to sinusoidal drivers. This applic...

  16. Attosecond quantum stroboscope.

    Science.gov (United States)

    Paulus, Gerhard G; Stania, Gernot

    2009-04-14

    Electron disco: A "quantum stroboscope" for capturing the electron motion on a subfemtosecond timescale for a particular class of problems is highlighted. The picture shows a diffraction pattern caused by wave packets obtained by synchronizing attosecond UV pulses to a near-IR field and ionizing rare-gas atoms. PMID:19294685

  17. Attosecond VUV Coherent Control of Molecular Dynamics

    CERN Document Server

    Ranitovic, P; Riviere, P; Palacios, A; Tong, X M; Toshima, N; Gonzalez-Castrillo, A; Martin, L; Martin, F; Murnane, M M; Kapteyn, H C

    2014-01-01

    High harmonic light sources make it possible to access attosecond time-scales, thus opening up the prospect of manipulating electronic wave packets for steering molecular dynamics. However, two decades after the birth of attosecond physics, the concept of attosecond chemistry has not yet been realized. This is because excitation and manipulation of molecular orbitals requires precisely controlled attosecond waveforms in the deep ultraviolet, which have not yet been synthesized. Here, we present a novel approach using attosecond vacuum ultraviolet pulse-trains to coherently excite and control the outcome of a simple chemical reaction in a deuterium molecule in a non-Born Oppenheimer regime. By controlling the interfering pathways of electron wave packets in the excited neutral and singly-ionized molecule, we unambiguously show that we can switch the excited electronic state on attosecond timescales, coherently guide the nuclear wave packets to dictate the way a neutral molecule vibrates, and steer and manipula...

  18. Propagation of attosecond electron bunches along the cone-and-channel target

    International Nuclear Information System (INIS)

    Generation and propagation of attosecond electron bunches along a cone-and-channel target are investigated by particle-in-cell simulation. The target electrons are pulled out by the oscillating electric field of an intense laser pulse irradiating a cone target and accelerated forward along the cone walls. It is shown that the energetic electrons can be further guided and confined by a channel attached to the cone tip. The propagation of these electrons along the channel induces a strong quasistatic magnetic field as well as a sheath electric field since a part of the energetic electrons expands into the surrounding vacuum. The electromagnetic field in turn confines the surface currents. With the cone-and-channel target the energetic electrons can be much better collimated and propagate much farther than that from the classical cone target.

  19. Intensity improvement in the attosecond pulse generation with the coherent superposition initial state

    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: tschu@dicp.ac.cn [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)

    2012-03-26

    We investigate the coherent superposition initial state effect and found that when the initial active electron state is prepared in the coherent superposition of the 1s and 2s states of the He{sup +} ion and the chirp parameter of the fundamental field in the two-color scheme is chosen to be β=0.3, the harmonic cutoff energy is remarkably extended and the harmonic yield is enhanced by at least 6 orders of magnitude compared with the case of the single 1s ground state with chirp-free pulse. An ultrabroad supercontinuum with a 458 eV bandwidth is formed, directly producing an intense isolated 34 as pulse. -- Highlights: ► Simulating the HHG process irradiated from a model He{sup +} ion in a two-color field. ► Preparing the initial active electronic state in the 1s and 2s superposition state. ► Finding the optimized chirp parameter of β=0.3 for the fundamental field. ► Observing the intensity enhancement in HHG with more than 6 orders of magnitude improvement. ► Generating a 34 as isolated attosecond pulse with similar intensity enhancement.

  20. Effects of dispersion and filtering induced by periodic multilayer mirrors reflection on attosecond pulses

    Science.gov (United States)

    Lin, Cheng-You; Yin, Liang; Chen, Shu-Jing; Chen, Zhao-Yang; Ding, Ying-Chun

    2016-09-01

    Using temporal and spectral methods, the effects of dispersion and filtering induced by Mo/Si multilayer mirrors reflection on incident attosecond pulses were studied. First, two temporal parameters, the pulse broadening factor, and the energy loss factor, were defined to evaluate the effects of dispersion and filtering. Then, by analyzing these temporal parameters, we investigated and compared the dispersion and filtering effects on attosecond pulses. In addition, we explored the origins of pulse broadening and energy loss by analyzing the spectral and temporal characteristics of periodic Mo/Si multilayer mirrors. The results indicate that the filtering effect induced by Mo/Si multilayer mirrors reflection is the dominant reason for pulse broadening and energy loss. Project supported by the National Natural Science Foundation of China (Grant Nos. 11547183 and 11547241) and the Fundamental Research Funds for Central Universities, China (Grant Nos. JD1517 and 2652014012).

  1. Laser plasma as a source of intense attosecond pulses via high-order harmonic generation

    International Nuclear Information System (INIS)

    The incredible progress in ultrafast laser technology and Ti:sapphire lasers have lead to many important applications, one of them being high-order harmonic generation (HHG). HHG is a source of coherent extreme ultraviolet (XUV) radiation, which has opened new frontiers in science by extending nonlinear optics and time-resolved spectroscopy to the XUV region, and pushing ultrafast science to the attosecond domain. Progress in attosecond science has revealed many new phenomena that have not been seen with femtosecond pulses. Clearly, the next frontier is to study nonlinear effects at the attosecond timescale and in the XUV. However, a problem with present-day attosecond pulses is that they are just too weak to induce measurable nonlinearities, which severely limits the application of this source. While HHG from solid targets has shown promise for higher conversion efficiency, there is no experiment so far that demonstrates isolated attosecond pulse generation. The generation of isolated, several 100-as pulses with few-µJ energy will enable us to enter a completely new phase in attoscience. In past works, we have demonstrated that high-order harmonics from lowly ionized plasma is a highly efficient method to generate coherent XUV pulses. For example, indium plasma has been shown to generate intense 13th harmonic of the Ti:sapphire laser, with conversion efficiency of 10-4. However, the quasi-monochromatic nature of indium harmonics would make it difficult to generate attosecond pulses. We have also demonstrated that one could increase the harmonic yield by using nanoparticle targets. Specifically, we showed that by using indium oxide nanoparticles or C60 film, we could obtain intense harmonics between wavelengths of 50 to 90 nm. The energy in each of these harmonic orders was measured to be a few µJ, which is sufficient for many applications. However, the problem of using nanoparticle or film targets is the rapid decrease in the harmonic intensity, due to the rapid

  2. Generation of isolated attosecond pulses with a specific waveform two-color laser field

    Institute of Scientific and Technical Information of China (English)

    Jinping Yao; Yao Li; Ya Cheng

    2011-01-01

    We theorotically propose a new methed for generating intense isolated attosceond pulses during high-order harmonic generation (HHG) process by accurately controlling electron motion with a two-color laser field,which consists of an, 8O0-nm, 4-fs elliptically pollarized laser field and a 1400-nm, ~43-fs linearly polarized laser field. With this method, the supercontinua with a spectral width above 200 eV are obtained, which call support a ~15-as isolated pulse after phase compensation Classical and quantum analyses explain the controlling effects well. In particular, when the pules duration of the 800-nm laser field increases to 20- fs,sub-1O0-as isolated pules can be obtained even without any phase compensation%@@ We theoretically propo8e a new method for generating intense isolated attosecond pulses during high-order harmonic generation (HHG) process by accurately controlling electron motion with a two-color laser field,which consists of an 800-nm, 4-fs elliptically polarized laser field and a 1400-nm, ~43-fs linearly polarized laser field.With this method, the supercontinua with a spectral width above 200 eV are obtained, which can support a ~15-as isolated pulse after phase compensation.Classical and quantum analyses explain the controlling effects well.In particular, when the puLse duration of the 800-nm laser field increases to 20-fs, sub-lOO-as isolated pulses can be obtained even without any phase compensation.

  3. EDITORIAL: Attosecond and x-ray free-electron laser physics Attosecond and x-ray free-electron laser physics

    Science.gov (United States)

    Moshammer, R.; Ullrich, J.

    2009-07-01

    Currently, we are witnessing a revolution in photon science, driven by the vision to time-resolve ultra-fast electronic motion in atoms, molecules, and solids as well as by the quest for the characterization of time-dependent structural changes in large molecules and solids. Quantum jumps in the development of light sources are the key technologies for this emerging field of research. Thus, high harmonic radiation bursts now penetrate the attosecond (10-18 s) regime and free-electron lasers (FELs) deliver ultra-brilliant femtosecond, coherent VUV and x-ray pulses. This special issue presents a snapshot of this ongoing revolution and brings together, for the first time, pioneering results in both of these fields that are expected to evolve synergetically in the future. The volume is based on the spirit of the International Conference on Multi-Photon Processes, ICOMP08, which was held at the Max Planck Institute for Nuclear Physics in Heidelberg in summer 2008. The first contributions include articles that envision tracing electronic motion on an attosecond time scale and its relation to nuclear motion. After more technical papers on the generation of attosecond pulses via high harmonic generation (HHG), molecular and two-electron atomic dynamics in strong optical fields at a typical wavelength of 800 nm are presented pointing to sub-cycle, attosecond features. Making the transition to shorter wavelengths, nonlinear dynamics in atoms and molecules is explored via experimental and theoretical methods, where the present measurements are nearly exclusively performed at FEL sources. A substantial number of articles focus on the investigation of the most simple many- (few-) photon two-electron processes in double ionization of helium at optical and VUV wavelengths, with the goal of characterizing this fundamental reaction, not yet consistently solved theoretically, in spite of huge efforts. Finally, the behaviour of more complex nanoscaled systems, i.e. clusters, is

  4. Isolated attosecond pulse generation with the chirped two-color laser field

    Science.gov (United States)

    Tai, Huiqin; Li, Fang; Wang, Zhe

    2016-07-01

    We propose a scheme to generate isolated attosecond pulse using a linearly chirped two-color laser field, which includes a fundamental laser field and a weak infrared control laser field in the multicycle regime. The fundamental laser field consists of one linearly up-chirped and one linearly down-chirped pulses. The control pulse is chirped free. We compare the attosecond pulse generated in the chirped two-color field and the chirp-free field. It is found that an IAP can be generated even without carrier envelop phase stabilization in the chirped two-color laser field with a duration of 40 fs. We also discuss the influence of the relative intensity, relative phase, time delay, and chirping parameters on the generation of IAPs.

  5. Two-Dimensional Attosecond Electron Wave Packet Interferometry

    CERN Document Server

    Xie, Xinhua

    2014-01-01

    We propose a two-dimensional interferometry based on electron wave packet interference with a cycle-shaped orthogonally polarized two-color laser field. With such method, sub-cycle and inter-cycle interferences can be disentangled into different direction in the measured photoelectron momentum spectra. With the cycle-shaped laser field, the Coulomb influence can be minimized and the overlapping of interference fringes with the complicate low-energy structures can be avoided as well. The contributions of excitation effect and long-range Coulomb potential can be traced in the Fourier domain of the photoelectron distributions. With these advantages, it allows to get precise information on valence electron dynamics of atoms or molecules with attosecond resolution and additional spatial information with angstrom resolution.

  6. Ionization of helium in the attosecond equivalent light pulse of 1 GeV/u U92+ projectiles

    International Nuclear Information System (INIS)

    Single and double ionization of helium by 1 GeV/u U92+ impact was explored in a kinematically complete experiment. The relativistic ion generates a sub-attosecond (10-18 s) superintense (I>1019 W/cm2) electromagnetic pulse, which is interpreted as a field of equivalent photons (Weizsaecker-Williams method). Cross sections, the emission characteristics of ions and electrons as well as momentum balances are quantitatively discussed in terms of photoionization of the atom in this broadband, ultra-short virtual photon field. (orig.)

  7. Efficient generation of isolated attosecond pulses with high beam-quality by two-color Bessel-Gauss beams

    CERN Document Server

    Wang, Zhe; Zhang, Qingbin; Wang, Shaoyi; Lu, Peixiang

    2011-01-01

    The generation of isolated attosecond pulses with high efficiency and high beam quality is essential for attosec- ond spectroscopy. We numerically investigate the supercontinuum generation in a neutral rare-gas medium driven by a two-color Bessel-Gauss beam. The results show that an efficient smooth supercontinuum in the plateau is obtained after propagation, and the spatial profile of the generated attosecond pulse is Gaussian-like with the divergence angle of 0.1 degree in the far field. This bright source with high beam quality is beneficial for detecting and controlling the microscopic processes on attosecond time scale.

  8. A-periodic multilayer development for attosecond pulses in the 300-500 eV photon energy range

    Energy Technology Data Exchange (ETDEWEB)

    Guggenmos, Alexander; Hofstetter, Michael; Kleineberg, Ulf [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Garching (Germany); Max-Planck-Institut fuer Quantenoptik, Garching (Germany); Rauhut, Roman [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Garching (Germany)

    2011-07-01

    The development of ultrafast X-ray pulses in the sub-femtosecond time regime is a cutting edge technology for studying electron dynamics in atoms, molecules or solid surfaces/nanostructures by means of pump/probe electron spectroscopy. XUV elements as multilayer mirrors and thin metal filters are used to filter and shape attosecond bursts from high harmonic radiation. One near future goal is to extend the current technology to higher photon energies, reaching the water window range around 300-500 eV, where the in-vitro investigation of bio-materials on ultra-short time scales becomes possible. Following the ideas of nowadays experimental setups, both the spectral and the temporal resolution can be determined and guided by means of periodic and a-periodic multilayer mirrors, allowing for spectral and temporal soft X-ray pulse shaping. We will present first investigations of periodic and a-periodic multilayer XUV optics in that energy range of 300-400 eV and discuss their applications for filtering single attosecond pulses from High Harmonic radiation. Simulations and optimizations of various binary and ternary multilayer material systems as well as first experimental results achieved by Ion Beam Deposition and in-situ ellipsometry of the deposited nanolayers are demonstrated.

  9. Two-photon finite-pulse model for resonant transitions in attosecond experiments

    CERN Document Server

    Galán, Álvaro Jiménez; Argenti, Luca

    2015-01-01

    We present an analytical model capable of describing two-photon ionization of atoms with attosecond pulses in the presence of intermediate and final isolated autoionizing states. The model is based on the finite-pulse formulation of second-order time-dependent perturbation theory. It approximates the intermediate and final states with Fano's theory for resonant continua, and it depends on a small set of atomic parameters that can either be obtained from separate \\emph{ab initio} calculations, or be extracted from few selected experiments. We use the model to compute the two-photon resonant photoelectron spectrum of helium below the N=2 threshold for the RABITT (Reconstruction of Attosecond Beating by Interference of Two-photon Transitions) pump-probe scheme, in which an XUV attosecond pulse train is used in association to a weak IR probe, obtaining results in quantitative agreement with those from accurate \\emph{ab initio} simulations. In particular, we show that: i) Use of finite pulses results in a homogene...

  10. Two-photon finite-pulse model for resonant transitions in attosecond experiments

    Science.gov (United States)

    Jiménez-Galán, Álvaro; Martín, Fernando; Argenti, Luca

    2016-02-01

    We present an analytical model capable of describing two-photon ionization of atoms with attosecond pulses in the presence of intermediate and final isolated autoionizing states. The model is based on the finite-pulse formulation of second-order time-dependent perturbation theory. It approximates the intermediate and final states with Fano's theory for resonant continua, and it depends on a small set of atomic parameters that can either be obtained from separate ab initio calculations or be extracted from a few selected experiments. We use the model to compute the two-photon resonant photoelectron spectrum of helium below the N =2 threshold for the RABITT (reconstruction of attosecond beating by interference of two-photon transitions) pump-probe scheme, in which an XUV attosecond pulse train is used in association with a weak IR probe, obtaining results in quantitative agreement with those from accurate ab initio simulations. In particular, we show that (i) the use of finite pulses results in a homogeneous redshift of the RABITT beating frequency, as well as a resonant modulation of the beating frequency in proximity to intermediate autoionizing states; (ii) the phase of resonant two-photon amplitudes generally experiences a continuous excursion as a function of the intermediate detuning, with either zero or 2 π overall variation.

  11. High Harmonic Radiation Generation and Attosecond pulse generation from Intense Laser-Solid Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Alexander Roy [Univ. of Michigan, Ann Arbor, MI (United States); Krushelnick, Karl [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-09-08

    We have studied ion motion effects in high harmonic generation, including shifts to the harmonics which result in degradation of the attosecond pulse train, and how to mitigate them. We have examined the scaling with intensity of harmonic emission. We have also switched the geometry of the interaction to measure, for the first time, harmonics from a normal incidence interaction. This was performed by using a special parabolic reflector with an on axis hole and is to allow measurements of the attosecond pulses using standard techniques. Here is a summary of the findings: First high harmonic generation in laser-solid interactions at 1021 Wcm-2, demonstration of harmonic focusing, study of ion motion effects in high harmonic generation in laser-solid interactions, and demonstration of harmonic amplification.

  12. Fractional high-harmonic combs by attosecond-precision split-spectrum pulse control

    Directory of Open Access Journals (Sweden)

    Laux Martin

    2013-03-01

    Full Text Available Few-cycle laser fields enable pulse-shaping control of high-order harmonic generation by time delaying variable broadband spectral sections. We report the experimental generation of fractional (noninteger high-harmonic combs by the controlled interference of two attosecond pulse trains. Additionally the energy of the high harmonics is strongly tuned with the relative time delay. We quantify the tuning to directly result from the controlled variation of the instantaneous laser frequency at the shaped driver pulse intensity maximum.

  13. Improving attosecond pulse reflection by large angle incidence for a periodic multilayer mirror in the extreme ultraviolet region

    Institute of Scientific and Technical Information of China (English)

    Lin Cheng-You; Chen Shu-Jing; Liu Da-He

    2013-01-01

    The improvement of attosecond pulse reflection by large angle incidence for a periodic multilayer mirror in the extreme ultraviolet region has been discussed.Numerical simulations of both spectral and temporal reflection characteristics of periodic multilayer mirrors under various incident angles have been analyzed and compared.It was found that the periodic multilayer mirror under a larger incidence angle can provide not only higher integrated reflectivity but also a broader reflection band with negligible dispersion,making it possible to obtain better a reflected pulse that has a higher pulse reflection efficiency and shorter pulse duration for attosecond pulse reflection.In addition,by increasing the incident angle,the promotion of attosecond pulse reflection capability has been proven for periodic multilayer mirrors with arbitrary layers.

  14. Broadband multilayer mirror and diffractive optics for attosecond pulse shaping in the 280-500 eV photon energy range

    Directory of Open Access Journals (Sweden)

    Schmidt J.

    2013-03-01

    Full Text Available Chirped broadband multilayer mirrors are key components to shape attosecond pulses in the XUV range. Compressing high harmonic pulses to their Fourier limit is the major goal for attosecond physics utilizing short pulse pump-probe experiments. Here, we report about the first implementation of multilayers and diffractive optics fulfilling these requirements in the “water-window” spectral range.

  15. Attosecond Lighthouses

    CERN Document Server

    Vincenti, H

    2011-01-01

    Coherent light beams composed of ultrashort pulses are now increasingly used in different fields of Science, from time-resolved spectroscopy to plasma physics. Under the effect of even simple optical components, the spatial properties of these beams can vary over the duration of the light pulse. In this letter, we show how such spatio-temporally coupled electromagnetic fields can be exploited to produce an attosecond lighthouse, i.e. a source emitting a collection of isolated attosecond pulses, propagating in angularly well-separated light beams. This very general effect not only opens the way to a new generation of attosecond light sources, particularly suitable for pump-probe experiments, but also provides a powerful new tool for ultrafast metrology, for instance giving direct access to fluctuations in the phase of the laser field oscillations with respect to the pulse envelop, right at the focus of even the most intense ultrashort laser beams.

  16. Attosecond control of electron-ion recollision in high harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Gademann, G; Kelkensberg, F; Siu, W K; Vrakking, M J J [FOM-Institute for Atomic and Molecular Physics (AMOLF), Science Park 104, 1098 XG Amsterdam (Netherlands); Johnsson, P [Department of Physics, Lund University, PO Box 118, SE-22100 Lund (Sweden); Gaarde, M B; Schafer, K J, E-mail: g.gademann@amolf.nl [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)

    2011-03-15

    We show that high harmonic generation driven by an intense near-infrared (IR) laser can be temporally controlled when an attosecond pulse train (APT) is used to ionize the generation medium, thereby replacing tunnel ionization as the first step in the well-known three-step model. New harmonics are formed when the ionization occurs at a well-defined time within the optical cycle of the IR field. The use of APT-created electron wave packets affords new avenues for the study and application of harmonic generation. In the present experiment, this makes it possible to study harmonic generation at IR intensities where tunnel ionization does not give a measurable signal.

  17. Attosecond control of electron-ion recollision in high harmonic generation

    Science.gov (United States)

    Gademann, G.; Kelkensberg, F.; Siu, W. K.; Johnsson, P.; Gaarde, M. B.; Schafer, K. J.; Vrakking, M. J. J.

    2011-03-01

    We show that high harmonic generation driven by an intense near-infrared (IR) laser can be temporally controlled when an attosecond pulse train (APT) is used to ionize the generation medium, thereby replacing tunnel ionization as the first step in the well-known three-step model. New harmonics are formed when the ionization occurs at a well-defined time within the optical cycle of the IR field. The use of APT-created electron wave packets affords new avenues for the study and application of harmonic generation. In the present experiment, this makes it possible to study harmonic generation at IR intensities where tunnel ionization does not give a measurable signal.

  18. Lanthanum-molybdenum multilayer mirrors for attosecond pulses between 80 and 130 eV

    Energy Technology Data Exchange (ETDEWEB)

    Hofstetter, M; Schultze, M; Guggenmos, A; Gagnon, J; Yakovlev, V S; Krausz, F; Kleineberg, U [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Am Coulombwall 1, 85748 Garching (Germany); Aquila, A; Yang, S; Gullikson, E [Center for X-Ray Optics, Lawrence Berkeley National Laboratory, 2-400, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Huth, M; Nickel, B [Center for NanoScience (CeNS), Ludwig-Maximilians-Universitaet Muenchen, Schellingstrasse 4, 80799 Munich (Germany); Goulielmakis, E, E-mail: michael.hofstetter@mpq.mpg.de [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany)

    2011-06-15

    A novel multilayer material system consisting of lanthanum and molybdenum nano-layers for both broadband and highly reflecting multilayer mirrors in the energy range between 80 and 130 eV is presented. The simulation and design of these multilayers were based on an improved set of optical constants, which were recorded by extreme ultraviolet (XUV)/soft-x-ray absorption measurements on freestanding lanthanum nano-films between 30 eV and 1.3 keV. Lanthanum-molybdenum (La/Mo) multilayer mirrors were produced by ion-beam sputtering and characterized through both x-ray and XUV reflectivity measurements. We demonstrate the ability to precisely simulate and realize aperiodic stacks. Their stability against ambient air conditions is demonstrated. Finally, the La/Mo mirrors were used in the generation of single attosecond pulses from high-harmonic cut-off spectra above 100 eV. Isolated 200 attosecond-long pulses were measured by XUV-pump/IR-probe streaking experiments and characterized using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG/CRAB) analyses.

  19. Laser Phase Determination and Transfer Function to Directly Measure the Temporal Structure of a Narrow Bandwidth Attosecond EUV Pulse

    Institute of Scientific and Technical Information of China (English)

    GE Yu-Cheng

    2006-01-01

    A laser phase determination method and a transfer function that includes a proportional term of a measured photoelectron energy spectrum are presented to directly measure the detailed temporal structure of a narrow bandwidth attosecond extreme-ultraviolet (EUV) pulse. The method is based on the spectrum measurement of an electron generated by EUV photo-ionization interacting with a femtosecond laser field. The results of the study suggest that measurements should be taken at 0° or 180° with respect to the linear laser polarization. The method has a temporal measurement range of about half a laser oscillation period. The temporal resolution also depends on the jitter and control precision of the laser and EUV pulses.

  20. Optimization of infrared two-color multicycle field synthesis for intense-isolated-attosecond-pulse generation

    Science.gov (United States)

    Lan, Pengfei; Takahashi, Eiji J.; Midorikawa, Katsumi

    2010-11-01

    We present the optimization of the two-color synthesis method for generating an intense isolated attosecond pulse (IAP) in the multicycle regime. By mixing an infrared assistant pulse with a Ti:sapphire main pulse, we show that an IAP can be produced using a multicycle two-color pulse with a duration longer than 30 fs. We also discuss the influence of the carrier-envelope phase (CEP) and the relative intensity on the generation of IAPs. By optimizing the wavelength of the assistant field, IAP generation becomes insensitive to the CEP slip. Therefore, the optimized two-color method enables us to relax the requirements of pulse duration and easily produce the IAP with a conventional multicycle laser pulse. In addition, it enables us to markedly suppress the ionization of the harmonic medium. This is a major advantage for efficiently generating intense IAPs from a neutral medium by applying the appropriate phase-matching and energy-scaling techniques.

  1. Charge migration induced by attosecond pulses in bio-relevant molecules

    Science.gov (United States)

    Calegari, Francesca; Trabattoni, Andrea; Palacios, Alicia; Ayuso, David; Castrovilli, Mattea C.; Greenwood, Jason B.; Decleva, Piero; Martín, Fernando; Nisoli, Mauro

    2016-07-01

    After sudden ionization of a large molecule, the positive charge can migrate throughout the system on a sub-femtosecond time scale, purely guided by electronic coherences. The possibility to actively explore the role of the electron dynamics in the photo-chemistry of bio-relevant molecules is of fundamental interest for understanding, and perhaps ultimately controlling, the processes leading to damage, mutation and, more generally, to the alteration of the biological functions of the macromolecule. Attosecond laser sources can provide the extreme time resolution required to follow this ultrafast charge flow. In this review we will present recent advances in attosecond molecular science: after a brief description of the results obtained for small molecules, recent experimental and theoretical findings on charge migration in bio-relevant molecules will be discussed.

  2. Attosecond lighthouses from plasma mirrors

    OpenAIRE

    A. Wheeler, Jonathan; Borot, Antonin; Monchocé, Sylvain; Vincenti, Henri; Ricci, Aurélien; Malvache, Arnaud; Lopez-Martens, Rodrigo B.; Quéré, Fabien

    2012-01-01

    International audience The nonlinear interaction of an intense femtosecond laser pulse with matter can lead to the emission of a train of sub-laser-cycle--attosecond--bursts of short-wavelength radiation1, 2. Much effort has been devoted to producing isolated attosecond pulses, as these are better suited to real-time imaging of fundamental electronic processes3, 4, 5, 6. Successful methods developed so far rely on confining the nonlinear interaction to a single sub-cycle event7, 8, 9. Here...

  3. Towards optical attosecond pulses: broadband phase coherence between an ultrafast laser and OPO using lock-tozero CEO stabilization

    Science.gov (United States)

    McCracken, R. A.; Sun, J.; Leburn, C. G.; Reid, D. T.

    2013-03-01

    The carrier-envelope-offset frequencies of the pump, signal, idler and related sum-frequency mixing pulses have been locked to 0 Hz in a 20-fs-Ti:sapphire-pumped optical parametric oscillator, satisfying a critical prerequisite for optical attosecond pulse synthesis.

  4. Isolated attosecond pulse by optimize the parameters of two-color combined field

    International Nuclear Information System (INIS)

    Based on the classical theory, in this paper we optimize the intensity ratio of basic frequency field and low frequency field in the combined field. Then solving time-dependent Schrodinger equation of one-dimensional model helium atom driven by the optimized combined field, we find that high-order harmonic generation cut-off position of helium atom is extended. In addition, taking into account the initial phase of the basic frequency field, we obtain an isolated sub-37 attosecond pulse from the high-order harmonic generation of Helium atom driven by the combined field. (authors)

  5. Quantum mechanical approach to probing the birth of attosecond pulses using a two-color field

    CERN Document Server

    Dahlström, J M; Mauritsson, J

    2011-01-01

    We investigate the generation of even and odd harmonics using an intense laser and a weak second harmonic field. Our theoretical approach is based on solving the saddle-point equations within the Strong Field Approximation. The phase of the even harmonic oscillation as a function of the delay between fundamental and second harmonic field is calculated and its variation with energy is found to be in good agreement with recent experimental results. We also find that the relationship between this phase variation and the group delay of the attosecond pulses, depends on the intensity and wavelength of the fundamental field as well as the ionization potential of the atom.

  6. A Novel Femtosecond Laser System for Attosecond Pulse Generation

    OpenAIRE

    Jianqiang Zhu; Xinglong Xie; Meizhi Sun; Qunyu Bi; Jun Kang

    2012-01-01

    We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA). The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the K...

  7. Attosecond physics at the nanoscale

    CERN Document Server

    Ciappina, M F; Landsman, A S; Okell, W; Zherebtsov, S; Förg, B; Schötz, J; Seiffert, J L; Fennel, T; Shaaran, T; Zimmermann, T; Chacón, A; Guichard, R; Zaïr, A; Tisch, J W G; Marangos, J P; Witting, T; Braun, A; Maier, S A; Roso, L; Krüger, M; Hommelhoff, P; Kling, M F; Krausz, F; Lewenstein, M

    2016-01-01

    Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds, which is comparable with the optical field. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this article we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spati...

  8. Manifestation of attosecond XUV fields temporal structures in attosecond streaking spectrogram

    Institute of Scientific and Technical Information of China (English)

    Guanglong Chen; Yunjiu Cao; Dong Eon Kim

    2011-01-01

    @@ The features of an attosecond extreme ultraviolet (XUV) field are encoded in the attosecond XUV spectrogram.We investigate the effect of the temporal structures of attosecond XUV fields on the attosecond streaking spectrogram.Factors such as the number of attosecond XUV pulses and the temporal chirp of attosecond XUV pulses are considered.Results indicate that unlike the attosecond streaking spectrogram for an attosecond XUV field with two pulses of a half-cycle separation of streaking field, the spectrogram for the attosecond XUV field with three pulses demonstrates fine spectral fringes in separated traces.%The features of an attosecond extreme ultraviolet (XUV) field are encoded in the attosecond XUV spectrogram. We investigate the effect of the temporal structures of attosecond XUV fields on the attosecond streaking spectrogram. Factors such as the number of attosecond XUV pulses and the temporal chirp of attosecond XUV pulses are considered. Results indicate that unlike the attosecond streaking spectrogram for an attosecond XUV field with two pulses of a half-cycle separation of streaking field, the spectrogram for the attosecond XUV field with three pulses demonstrates fine spectral fringes in separated traces.

  9. Controls for the generation of high-order harmonics and attosecond pulses by an infrared laser field combined with a low-frequency pulse

    Institute of Scientific and Technical Information of China (English)

    He Hai-Xiang; Guo Ya-Hui; He Guo-Zhong

    2012-01-01

    We investigate high-order harmonic generations by controlling various quantum paths of harmonics in an infrared laser field which combines a low-frequency pulse.Both classical theory and the quantum wavelet transform method are used to understand the physics of harmonics.By adjusting the carrier envelope phase of the fundamental field,the intensities of harmonic spectra increase and the harmonics in the plateau become regular.Attosecond pulses each with a duration of 58 as are obtained directly by compressing the harmonics,and with phase compensation an isolated attosecond pulse less than 30 as can be generated.

  10. Two-photon double ionization of neon using an intense attosecond pulse train

    CERN Document Server

    Manschwetus, B; Campi, F; Maclot, S; Coudert-Alteirac, H; Lahl, J; Wikmark, H; Rudawski, P; Heyl, C M; Farkas, B; Mohamed, T; L'Huillier, A; Johnsson, P

    2016-01-01

    We present the first demonstration of two-photon double ionization of neon using an intense extreme ultraviolet (XUV) attosecond pulse train (APT) in a photon energy regime where both direct and sequential mechanisms are allowed. For an APT generated through high-order harmonic generation (HHG) in argon we achieve a total pulse energy close to 1 $\\mu$J, a central energy of 35 eV and a total bandwidth of $\\sim30$ eV. The APT is focused by broadband optics in a neon gas target to an intensity of $3\\cdot10^{12} $W$\\cdot$cm$^{-2}$. By tuning the photon energy across the threshold for the sequential process the double ionization signal can be turned on and off, indicating that the two-photon double ionization predominantly occurs through a sequential process. The demonstrated performance opens up possibilities for future XUV-XUV pump-probe experiments with attosecond temporal resolution in a photon energy range where it is possible to unravel the dynamics behind direct vs. sequential double ionization and the asso...

  11. High-Order Harmonic Extension and Generation of Single Isolated Attosecond Pulse in Hydrogen Gas by Using Plasmonic Field Enhancement

    Directory of Open Access Journals (Sweden)

    Mojtaba Taghipour Kaffash, Neda Anvari, Saeed Batebi

    2014-01-01

    Full Text Available Recent advances in laser technology have enabled the full control of few-cycle optical fields, which have key applications including the production of isolated, attosecond (1as=10 -18s extreme ultraviolet (XUV pulses via high-harmonic generation (HHG [i] and the study of nanosystems in the ultrafast regime[ii,iii].

  12. Attosecond double-slit experiment.

    Science.gov (United States)

    Lindner, F; Schätzel, M G; Walther, H; Baltuska, A; Goulielmakis, E; Krausz, F; Milosević, D B; Bauer, D; Becker, W; Paulus, G G

    2005-07-22

    A new scheme for a double-slit experiment in the time domain is presented. Phase-stabilized few-cycle laser pulses open one to two windows (slits) of attosecond duration for photoionization. Fringes in the angle-resolved energy spectrum of varying visibility depending on the degree of which-way information are measured. A situation in which one and the same electron encounters a single and a double slit at the same time is observed. The investigation of the fringes makes possible interferometry on the attosecond time scale. From the number of visible fringes, for example, one derives that the slits are extended over about 500 as.

  13. Design of broadband transmission quarter-wave plates for polarization control of isolated attosecond pulses

    International Nuclear Information System (INIS)

    Using a standard Levenberg–Marquardt algorithm, broadband quarter-wave plates (QWPs) with bandwidth from 3 to 18 eV in the extreme ultraviolet (EUV) region were designed using aperiodic Mo/Si multilayers. By analyzing the design results of the Mo/Si multiayers with different bilayer numbers, we found that a Mo/Si multilayer with more bilayers can achieve broader phase control, but suffers from lower total throughput and a degree of circular polarization. In addition, the pulse broadenings caused by the group delay dispersions of the designed broadband QWPs were studied, and their layer distributions were investigated. The oscillating distribution of bilayer thickness in optimized multilayers was observed, which is considered to be the reason for forming the broadband phase control. Such broadband QWPs can be applied to generate a circularly polarized broadband EUV source, such as isolated attosecond pulse, directly from a linearly polarized source. (paper)

  14. Quantum path control and isolated attosecond pulse generation in the combination of near-infrared and terahertz pulses

    Science.gov (United States)

    Zhong, Hui-Ying; Guo, Jing; Zhang, Hong-Dan; Du, Hui; Liu, Xue-Shen

    2015-07-01

    We present an efficient and realizable scheme for the generation of an ultrashort single attosecond (as) pulse from H atom with a 800-nm fundamental laser field combined with a terahertz (THz) field. The high-order harmonic generation (HHG) can be obtained by solving the time-dependent Schrödinger equation accurately and efficiently with time-dependent generalized pseudo-spectral (TDGPS) method. The result shows that the plateau of high-order harmonics is extended and the broadband spectra can be produced by the combined laser pulse, which can be explained by the corresponding ionization probability. The time-frequency analysis and semi-classical three-step model are also presented to further investigate this mechanism. Besides, by the superposition of the harmonics near the cutoff region, an isolated 133-as pulse can be obtained. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174108, 11104108, and 11271158).

  15. Attosecond Quantum-Beat Spectroscopy in Helium

    CERN Document Server

    Shivaram, Niranjan; Timmers, Henry; Sandhu, Arvinder

    2015-01-01

    The evolution of electron wavepackets determines the course of many physical and chemical phenomena and attosecond spectroscopy aims to measure and control such dynamics in real-time. Here, we investigate radial electron wavepacket motion in Helium by using an XUV attosecond pulse train to prepare a coherent superposition of excited states and a delayed femtosecond IR pulse to ionize them. Quantum beat signals observed in the high resolution photoelectron spectrogram allow us to follow the field-free evolution of the bound electron wavepacket and determine the time-dependent ionization dynamics of the low-lying 2p state.

  16. Attosecond-correlated dynamics of two electrons in argon

    Indian Academy of Sciences (India)

    V Sharma; N Camus; B Fischer; M Kremer; A Rudenko; B Bergues; M Kuebel; N G Johnson; M F Kling; T Pfeifer; J Ullrich; R Moshammer

    2014-01-01

    In this work we explored strong field-induced decay of doubly excited transient Coulomb complex Ar** → Ar2++2. We measured the correlated two-electron emission as a function of carrier envelop phase (CEP) of 6 fs pulses in the non-sequential double ionization (NSDI) of argon. Classical model calculations suggest that the intermediate doubly excited Coulomb complex loses memory of its formation dynamics. We estimated the ionization time difference between the two electrons from NSDI of argon and it is 200 ± 100 as (N Camus et al, Phys. Rev. Lett. 108, 073003 (2012)).

  17. Attosecond electron-electron collision dynamics of the four-electron escape in Be close to threshold

    CERN Document Server

    Emmanouilidou, A

    2012-01-01

    We explore the escape geometry of four electrons a few eV above threshold following single-photon absorption from the ground state of Be. We find that the four electrons leave the atom on the vertices of a pyramid instead of a previously-predicted tetrahedron. To illustrate the physical mechanisms of quadruple ionization we use a momentum transferring attosecond collision scheme which we show to be in accord with the pyramid break-up pattern.

  18. EDITORIAL: Focus on Attosecond Physics

    Science.gov (United States)

    Bandrauk, André D.; Krausz, Ferenc; Starace, Anthony F.

    2008-02-01

    Investigations of light-matter interactions and motion in the microcosm have entered a new temporal regime, the regime of attosecond physics. It is a main 'spin-off' of strong field (i.e., intense laser) physics, in which nonperturbative effects are fundamental. Attosecond pulses open up new avenues for time-domain studies of multi-electron dynamics in atoms, molecules, plasmas, and solids on their natural, quantum mechanical time scale and at dimensions shorter than molecular and even atomic scales. These capabilities promise a revolution in our microscopic knowledge and understanding of matter. The recent development of intense, phase-stabilized femtosecond (10-15 s) lasers has allowed unparalleled temporal control of electrons from ionizing atoms, permitting for the first time the generation and measurement of isolated light pulses as well as trains of pulses on the attosecond (1 as = 10-18 s) time scale, the natural time scale of the electron itself (e.g., the orbital period of an electron in the ground state of the H atom is 152 as). This development is facilitating (and even catalyzing) a new class of ultrashort time domain studies in photobiology, photochemistry, and photophysics. These new coherent, sub-fs pulses carried at frequencies in the extreme ultraviolet and soft-x-ray spectral regions, along with their intense, synchronized near-infrared driver waveforms and novel metrology based on sub-fs control of electron-light interactions, are spawning the new science of attosecond physics, whose aims are to monitor, to visualize, and, ultimately, to control electrons on their own time and spatial scales, i.e., the attosecond time scale and the sub-nanometre (Ångstrom) spatial scale typical of atoms and molecules. Additional goals for experiment are to advance the enabling technologies for producing attosecond pulses at higher intensities and shorter durations. According to theoretical predictions, novel methods for intense attosecond pulse generation may in

  19. Catching Conical Intersections in the Act; Monitoring Transient Electronic Coherences by Attosecond Stimulated X-Ray Raman Signals

    CERN Document Server

    Kowalewski, Markus; Dorfman, Konstantin E; Mukamel, Shaul

    2015-01-01

    Conical intersections (CoIn) dominate the pathways and outcomes of virtually all photophysical and photochemical molecular processes. Despite extensive experimental and theoretical effort, CoIns have not been directly observed yet and the experimental evidence is being inferred from fast reaction rates and some vibrational signatures. We show that short X-ray (rather than optical) pulses can directly detect the passage through a CoIn with the adequate temporal and spectral sensitivity. The technique is based on a coherent Raman process that employs a composite femtosecond/attosecond X-ray pulse to detect the electronic coherences (rather than populations) that are generated as the system passes through the CoIn.

  20. Phase measurement of a Fano window resonance using tunable attosecond pulses

    CERN Document Server

    Kotur, M; Jimenez-Galan, A; Kroon, D; Larsen, E W; Louisy, M; Bengtsson, S; Miranda, M; Mauritsson, J; Arnold, C L; Canton, S E; Gisselbrecht, M; Carette, T; Dahlstrom, J M; Lindroth, E; Maquet, A; Argenti, L; Martin, F; L'Huillier, A

    2015-01-01

    We study the photoionization of argon atoms close to the 3s$^2$3p$^6$ $\\rightarrow$ 3s$^1$3p$^6$4p $\\leftrightarrow$ 3s$^2$3p$^5$ $\\varepsilon \\ell$, $\\ell$=s,d Fano window resonance. An interferometric technique using an attosecond pulse train, i.e. a frequency comb in the extreme ultraviolet range, and a weak infrared probe field allows us to study both amplitude and phase of the photoionization probability amplitude as a function of photon energy. A theoretical calculation of the ionization process accounting for several continuum channels and bandwidth effects reproduces well the experimental observations and shows that the phase variation of the resonant two-photon amplitude depends on the interaction between the channels involved in the autoionization process.

  1. Attosecond streaking measurement of extreme ultraviolet pulses using a long-wavelength electric field

    Science.gov (United States)

    Saito, Nariyuki; Ishii, Nobuhisa; Kanai, Teruto; Watanabe, Shuntaro; Itatani, Jiro

    2016-01-01

    Long-wavelength lasers have great potential to become a new-generation drive laser for tabletop coherent light sources in the soft X-ray region. Because of the significantly low conversion efficiency from a long-wavelength light field to high-order harmonics, their pulse characterization has been carried out by measuring the carrier-envelope phase and/or spatial dependences of high harmonic spectra. However, these photon detection schemes, in general, have difficulty in obtaining information on the spectral phases, which is crucial to determine the temporal structures of high-order harmonics. Here, we report the first attosecond streaking measurement of high harmonics generated by few-cycle optical pulses at 1.7 μm from a BiB3O6–based optical parametric chirped-pulse amplifier. This is also the first demonstration of time-resolved photoelectron spectroscopy using high harmonics from a long-wavelength drive laser other than Ti:sapphire lasers, which paves the way towards ultrafast soft X-ray photoelectron spectroscopy. PMID:27752115

  2. Influence of vibrational states on high-order-harmonic generation and an isolated attosecond pulse from a N2 molecule

    Science.gov (United States)

    Guo, Jing; Ge, Xin-Lei; Zhong, Huiying; Zhao, Xi; Zhang, Meixia; Jiang, Yuanfei; Liu, Xue-Shen

    2014-11-01

    The high-order-harmonic generation (HHG) from the N2 molecule in an intense laser field is investigated by applying the Lewenstein method. The initial state is constructed as a linear combination of the highest occupied molecular orbital (HOMO) and the lower-lying orbital below the HOMO, which is well described by a Gaussian wave packet generated by using the gamess-uk package. The HHG with different vibrational states of N2 are calculated and our results show that the harmonic intensity can be enhanced by higher vibrational states, which can be explained by the ionization probability. We also compared the cases with a different full width at half maximum of laser fields together, which can be well understood by the time-frequency analysis and the three-step model. Finally, the attosecond pulse generation is studied with different vibrational states, where a series of attosecond pulses can be produced with the shortest being 91 as.

  3. A flexible apparatus for attosecond photoelectron spectroscopy of solids and surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Magerl, E.; Stanislawski, M.; Uphues, Th. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Neppl, S.; Barth, J. V.; Menzel, D.; Feulner, P. [Physik Department E20, Technische Universitaet Muenchen, James-Franck-Strasse, 85748 Garching (Germany); Cavalieri, A. L. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Max-Planck Research Department for Structural Dynamics, Universitaet Hamburg, Notkestrasse 85, 22607 Hamburg (Germany); Bothschafter, E. M.; Ernstorfer, R.; Kienberger, R. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Physik Department E11, Technische Universitaet Muenchen, James-Franck-Strasse, 85748 Garching (Germany); Hofstetter, M.; Kleineberg, U.; Krausz, F. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Ludwig-Maximilians-Universitaet Muenchen, Fakultaet fuer Physik, Am Coulombwall 1, 85748 Garching (Germany)

    2011-06-15

    We describe an apparatus for attosecond photoelectron spectroscopy of solids and surfaces, which combines the generation of isolated attosecond extreme-ultraviolet (XUV) laser pulses by high harmonic generation in gases with time-resolved photoelectron detection and surface science techniques in an ultrahigh vacuum environment. This versatile setup provides isolated attosecond pulses with photon energies of up to 140 eV and few-cycle near infrared pulses for studying ultrafast electron dynamics in a large variety of surfaces and interfaces. The samples can be prepared and characterized on an atomic scale in a dedicated flexible surface science end station. The extensive possibilities offered by this apparatus are demonstrated by applying attosecond XUV pulses with a central photon energy of {approx}125 eV in an attosecond streaking experiment of a xenon multilayer grown on a Re(0001) substrate.

  4. Diagrammatic approach to attosecond delays in photoionization

    CERN Document Server

    Dahlström, J M; Lindroth, E

    2012-01-01

    We study laser-assisted photoionization by attosecond pulses using a time-independent formalism based on diagrammatic many-body perturbation theory. Our aim is to provide an ab inito route to the "delays" for this above-threshold ionization process, which is essential for a quantitative understanding of attosecond metrology. We present correction curves for characterization schemes of attosecond pulses, such as "streaking", that account for the delayed atomic response in ionization from neon and argon. We also verify that photoelectron delays from many-electron atoms can be measured using similar schemes if, instead, the so-called continuum--continuum delay is subtracted. Our method is general and it can be extended also to more complex systems and additional correlation effects can be introduced systematically.

  5. Catching Conical Intersections in the Act; Monitoring Transient Electronic Coherences by Attosecond Stimulated X-Ray Raman Signals

    Science.gov (United States)

    Bennett, Kochise; Kowalewski, Markus; Dorfman, Konstantin; Mukamel, Shaul

    Conical intersections (CIs) dominate the pathways and outcomes of virtually all photochemical molecular processes. Despite extensive experimental and theoretical effort, CIs have not been directly observed yet and the experimental evidence is inferred from fast reaction rates and vibrational signatures. We show that short X-ray pulses can directly detect the passage through a CI with the adequate temporal and spectral sensitivity. The non-adiabatic coupling that exists in the region of a CI redistributes electronic population but also generates electronic coherence. This coherent oscillation can then be detected via a coherent Raman process that employs a composite femtosecond/attosecond X-ray pulse. This technique, dubbed Transient Redistribution of Ultrafast Electronic Coherences (TRUECARS) is reminiscent of Coherent Anti-Stokes Raman Spectroscopy (CARS) in that a coherent oscillation is set in motion and then monitored, but differs in that the dynamics is electronic (CARS generally observes nuclear dynamics) and the coherence is generated internally by passage through a region of non-adiabatic coupling rather than by an externally applied laser. Support provided by U.S. Department of Energy through Award No. DE-FG02-04ER15571, the National Science Foundation (Grant No CHE-1361516), and the Alexander von Humboldt foundation through the Feodor Lynen program.

  6. Rotations of molecular photoelectron angular distributions in above threshold ionization of H2+ by intense circularly polarized attosecond UV laser pulses

    International Nuclear Information System (INIS)

    We present molecular photoelectron angular distributions (MPADs) in multi-photon ionization processes by circularly polarized attosecond UV laser pulses. Simulations are performed on the single electron aligned molecular ion H2+ by solving corresponding 3D time-dependent Schrödinger equations. Numerical results of molecular above threshold ionization (MATI) show that rotations of MPADs with respect to the molecular and polarization axes depend on pulse intensities and photoelectron kinetic energies. We attribute the rotation to Γ, the difference between parallel and perpendicular ionization probabilities. It is found that in a resonant ionization process, the rotation angle is also a function of the symmetry of intermediate electronic states. The coherent population transfer between the initial and the resonant electronic states is controlled by pulse intensities. Such dependence of rotations on the pulse intensity is absent in Rydberg resonant ionizations as well as in MATI at large energy photons ℏω > Ip, where ω is angular frequency of photons and Ip is the molecular ionization potential. We describe these processes by a multi-photon perturbation theory model. Effects of molecular alignment and pulse ellipticities on rotations are investigated, confirming the essence of the ionization parameter Γ in rotations of MPADs. (paper)

  7. 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.

  8. Fundamentals of attosecond optics

    CERN Document Server

    Chang, Zenghu

    2011-01-01

    Attosecond optical pulse generation, along with the related process of high-order harmonic generation, is redefining ultrafast physics and chemistry. A practical understanding of attosecond optics requires significant background information and foundational theory to make full use of these cutting-edge lasers and advance the technology toward the next generation of ultrafast lasers. Fundamentals of Attosecond Optics provides the first focused introduction to the field. The author presents the underlying concepts and techniques required to enter the field, as well as recent research advances th

  9. Attosecond-resolution two-electron harmonic emission

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Liqiang [College of Science, Liaoning University of Technology, Jinzhou 121000 (China); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Li, Wenliang; Yuan, Minghu [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Duan, Yunbo [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); 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)

    2015-04-17

    Highlights: • A two-electron time-dependent Schrödinger equation analysis. • Harmonic emission spectrum from the neutral He atom in intense laser field. • An extended harmonic plateau with many new harmonic cutoffs. • A propose model of double recombination arising from electron correlation effect. • A general characteristic of double recombination in the two-electron system. - Abstract: Two-electron harmonic emission from the He atom has been investigated by solving the two-electron time-dependent Schrödinger equation (TDSE), which exhibits an extended plateau and many new harmonic cutoffs beyond the classical single-electron harmonic cutoff. Theoretical analyses show that these extended new cutoffs are caused by the sequential double recombination and the nonsequential double recombination of the two electrons, which is a general characteristic for the two-electron harmonic emission and which is revealed through the investigation on laser parameter effects. Moreover, from analyzing the time-dependent wave functions, the motions of the two electrons and the single and double ionization time have been described.

  10. Energy Sharing in the 2-Electron Attosecond Streak Camera

    CERN Document Server

    Price, H; Emmanouilidou, A

    2011-01-01

    Using the recently developed concept of the 2-electron streak camera (see NJP 12, 103024 (2010)), we have studied the energy-sharing between the two ionizing electrons in single-photon double ionization of He(1s2s). We find that the most symmetric and asymmetric energy sharings correspond to different ionization dynamics with the ion's Coulomb potential significantly influencing the latter. This different dynamics for the two extreme energy sharings gives rise to different patterns in asymptotic observables and different time-delays between the emission of the two electrons. We show that the 2-electron streak camera resolves the time-delays between the emission of the two electrons for different energy sharings.

  11. Propagation effects of isolated attosecond pulse generation with a multicycle chirped and chirped-free two-color field

    Energy Technology Data Exchange (ETDEWEB)

    Du Hongchuan; Hu Bitao [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China)

    2011-08-15

    We present a theoretical study of isolated attosecond pulse generation with a multicycle chirped and chirped-free two-color field. We show that the bandwidth of the extreme ultraviolet supercontinuum can be extended by combining a multicycle chirped pulse and a multicycle chirped-free pulse. Also, the broadband supercontinuum can still be generated when the macroscopic effects are included. Furthermore, the macroscopic effects can ameliorate the temporal characteristic of the broadband supercontinuum of the single atom, and eliminate the modulations of the broadband supercontinuum. Thus a very smooth broadband supercontinuum and a pure isolated 102-as pulse can be directly obtained. Moreover, the structure of the broadband supercontinuum can be steadily maintained for a relative long distance after a certain distance.

  12. MeV femtosecond electron pulses from direct-field acceleration in low density atomic gases

    CERN Document Server

    Varin, Charles; Hogan-Lamarre, Pascal; Fennel, Thomas; Piché, Michel; Brabec, Thomas

    2015-01-01

    Using three-dimensional particle-in-cell simulations, we show that few-MeV electrons can be produced by focusing tightly few-cycle radially-polarized laser pulses in a low-density atomic gas. In particular, it is observed that for the few-TW laser power needed to reach relativistic electron energies, longitudinal attosecond microbunching occurs naturally, resulting in femtosecond structures with high-contrast attosecond density modulations. The three-dimensional particle-in-cell simulations show that in the relativistic regime the leading pulse of these attosecond substructures survives to propagation over extended distances, suggesting that it could be delivered to a distant target, with the help of a properly designed transport beamline.

  13. Attosecond timing jitter pulse trains from semiconductor saturable absorber mode-locked Cr:LiSAF lasers

    OpenAIRE

    Sennaroğlu, Alphan; Li, Duo; Demirbaş, Ümit; Benedick, Andrew; Fujimoto, James G.; Kaertner, Franz X.

    2012-01-01

    The timing jitter of optical pulse trains from diode-pumped, semiconductor saturable absorber mode-locked femtosecond Cr:LiSAF lasers is characterized by a single-crystal balanced optical cross-correlator with an equivalent sensitivity in phase noise of -235 dBc/Hz. The RMS timing jitter is 30 attoseconds integrated from 10 kHz to 50 MHz, the Nyquist frequency of the 100 MHz repetition rate oscillator. The AM-to-PM conversion induced excess phase noise is calculated and compared with experime...

  14. 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).

  15. Complex Spectra Structure of an Attosecond Pulse Train Driven by Sub-5-fs Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    YUN Chen-Xia; TENG Hao; ZHANG Wei; WANG Li-Feng; ZHAN Min-Jie; HE Xin-Kui; WANG Bing-Bing; WEI Zhi-Yi

    2011-01-01

    We present the observation of the additional spectral components between the odd order harmonics in the harmonic spectrum generated from argon gas driven by sub-5-fs laser pulses.The theoretical analysis shows that the asymmetric laser field in both spatial and temporal domains leads to this complicated spectrum structure of high order harmonics.

  16. Eliminating the dipole phase in attosecond pulse characterization using Rydberg wave packets

    Science.gov (United States)

    Pabst, Stefan; Dahlström, Jan Marcus

    2016-07-01

    We propose a technique to fully characterize the temporal structure of extreme ultraviolet pulses by ionizing a bound coherent electronic wave packet. The influence of the dipole phase, which is the main obstacle for state-of-the-art pulse characterization schemes, can be eliminated by angle integration of the photoelectron spectrum. We show that in particular, atomic Rydberg wave packets are ideal and that wave packets involving multiple electronic states provide redundant information that can be used to cross-check the consistency of the phase reconstruction.

  17. Attosecond Coherent Control of the Photo-Dissociation of Oxygen Molecules

    Science.gov (United States)

    Sturm, Felix; Ray, Dipanwita; Wright, Travis; Shivaram, Niranjan; Bocharova, Irina; Slaughter, Daniel; Ranitovic, Predrag; Belkacem, Ali; Weber, Thorsten

    2016-05-01

    Attosecond Coherent Control has emerged in recent years as a technique to manipulate the absorption and ionization in atoms as well as the dissociation of molecules on an attosecond time scale. Single attosecond pulses and attosecond pulse trains (APTs) can coherently excite multiple electronic states. The electronic and nuclear wave packets can then be coupled with a second pulse forming multiple interfering quantum pathways. We have built a high flux extreme ultraviolet (XUV) light source delivering APTs based on HHG that allows to selectively excite neutral and ion states in molecules. Our beamline provides spectral selectivity and attosecond interferometric control of the pulses. In the study presented here, we use APTs, generated by High Harmonic Generation in a high flux extreme ultraviolet light source, to ionize highly excited states of oxygen molecules. We identify the ionization/dissociation pathways revealing vibrational structure with ultra-high resolution ion 3D-momentum imaging spectroscopy. Furthermore, we introduce a delay between IR pulses and XUV/IR pulses to constructively or destructively interfere the ionization and dissociation pathways, thus, enabling the manipulation of both the O2+and the O+ ion yields with attosecond precision. Supported by DOE under Contract No. DE-AC02-05CH11231.

  18. Attosecond Interference Induced by Coulomb-Field-Driven Transverse Backward-Scattering Electron Wave-Packets

    CERN Document Server

    Song, Xiaohong; Lin, Cheng; Sheng, Zhihao; Yu, Xianhuan; Yang, Weifeng; Hu, Shilin; Chen, Jing; Xu, SongPo; Chen, YongJu; Quan, Wei; Liu, XiaoJun

    2016-01-01

    A novel and universal interference structure is found in the photoelectron momentum distribution of atoms in intense infrared laser field. Theoretical analysis shows that this structure can be attributed to a new form of Coulomb-field-driven backward-scattering of photoelectrons in the direction perpendicular to the laser field, in contrast to the conventional rescattering along the laser polarization direction. This transverse backward-scattering process is closely related to a family of photoelectrons initially ionized within a time interval of less than 200 attosecond around the crest of the laser electric field. Those electrons, acquiring near-zero return energy in the laser field, will be pulled back solely by the ionic Coulomb field and backscattered in the transverse direction. Moreover, this rescattering process mainly occurs at the first or the second return times, giving rise to different phases of the photoelectrons. The interference between these photoelectrons leads to unique curved interference ...

  19. Attosecond Electro-Magnetic Forces Acting on Metal Nanospheres Induced By Relativistic Electrons

    Science.gov (United States)

    Lagos, M. J.; Batson, P. E.; Reyes-Coronado, A.; Echenique, P. M.; Aizpurua, J.

    2014-03-01

    Swift electron scattering near nanoscale materials provides information about light-matter behavior, including induced forces. We calculate time-dependent electromagnetic forces acting on 1-1.5 nm metal nanospheres induced by passing swift electrons, finding both impulse-like and oscillatory response forces. Initially, impulse-like forces are generated by a competition between attractive electric forces and repulsive magnetic forces, lasting a few attoseconds (5-10 as). Oscillatory, plasmonic response forces take place later in time, last a few femtoseconds (1- 5 fs), and apparently rely on photon emission by decay of the electron-induced surface plasmons. A comparison of the strength of these two forces suggests that the impulse-like behavior dominates the process, and can transfer significant linear momentum to the sphere. Our results advance understanding of the physics behind the observation of both attractive and repulsive behavior of gold nano-particles induced by electron beams in aberration-corrected electron microscopy. Work supported under DOE, Award # DE-SC0005132, Basque Gov. project ETORTEK inano, Spanish Ministerio de Ciencia e Innovacion, No. FIS2010-19609-C02-01.

  20. Electron dynamics in strong laser pulse illumination of large rare gas clusters

    Science.gov (United States)

    Saalmann, U.; Rost, J. M.

    2005-11-01

    We analyze the dynamics of up to 105 electrons resulting from illuminating a xenon cluster with 9093 atoms with intense laser pulses of different length and peak intensity. Interesting details of electron motion are identified which can be probed with a time resolution of 100 attoseconds. Corresponding experiments would shed light on unexplored territory in complex electronic systems such as clusters and they would also permit to critically access the present theoretical description of this dynamics.

  1. Attosecond physics at a nanoscale metal tip

    Directory of Open Access Journals (Sweden)

    Lemell Christoph

    2013-03-01

    Full Text Available With few-cycle laser oscillator pulses at 800 nm we observe strong-field and attosecond physics phenomena in electron spectra recorded at a nanoscale tungsten tip. We observe the rescattering plateau as well as a strong carrier-envelope phase dependence of the spectra. We model the results with the semiclassical three-step model as well as with time-dependent density functional theory.

  2. Helicity-selective phase-matching and quasi-phase matching of circularly polarized high-order harmonics: towards chiral attosecond pulses

    Science.gov (United States)

    Kfir, Ofer; Grychtol, Patrik; Turgut, Emrah; Knut, Ronny; Zusin, Dmitriy; Fleischer, Avner; Bordo, Eliyahu; Fan, Tingting; Popmintchev, Dimitar; Popmintchev, Tenio; Kapteyn, Henry; Murnane, Margaret; Cohen, Oren

    2016-06-01

    Phase matching of circularly polarized high-order harmonics driven by counter-rotating bi-chromatic lasers was recently predicted theoretically and demonstrated experimentally. In that work, phase matching was analyzed by assuming that the total energy, spin angular momentum and linear momentum of the photons participating in the process are conserved. Here we propose a new perspective on phase matching of circularly polarized high harmonics. We derive an extended phase matching condition by requiring a new propagation matching condition between the classical vectorial bi-chromatic laser pump and harmonics fields. This allows us to include the influence of the laser pulse envelopes on phase matching. We find that the helicity dependent phase matching facilitates generation of high harmonics beams with a high degree of chirality. Indeed, we present an experimentally measured chiral spectrum that can support a train of attosecond pulses with a high degree of circular polarization. Moreover, while the degree of circularity of the most intense pulse approaches unity, all other pulses exhibit reduced circularity. This feature suggests the possibility of using a train of attosecond pulses as an isolated attosecond probe for chiral-sensitive experiments.

  3. 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.

  4. Frequency-resolved optical gating for complete reconstruction of attosecond bursts : FROG CRAB

    International Nuclear Information System (INIS)

    Full text: We will show that when an atom is ionized by an XUV pulse in the presence of a low frequency laser field, this laser field acts as an ultrafast electron phase modulator on the electron wave-packet generated in the continuum. This phase modulator has a very large bandwidth and enables to transpose the most efficient techniques used for the temporal characterization of femtosecond pulses - such as SPIDER, FROG, or chronocyclic tomography - to attosecond fields, via continuum electron wave-packets replicas of these fields. We will then detail some of the attosecond metrology techniques derived from this general principle. We will especially insist on a recently proposed technique, FROG CRAB, which allows the complete temporal characterization of arbitrarily complex attosecond fields. FROG CRAB is direct transposition of Frequency-Resolved Optical Gating to attosecond electron wave-packets, using a femtosecond laser pulse as a phase gate. All the experimental tools for the implementation of CRAB are available. Besides its technical interest, CRAB establishes a direct connection between the main attosecond characterization techniques demonstrated experimentally so far, and considerably extends their scope, thus providing a general perspective on attosecond metrology. Refs. 2 (author)

  5. Production and Characterization of Attosecond Bunch Trains

    Energy Technology Data Exchange (ETDEWEB)

    Sears, Christopher M.S.; Colby, Eric; Ischebeck, Rasmus; McGuinness , Christopher; Nelson, Janice; Noble, Robert; Siemann, Robert H.; Spencer, James; Walz, Dieter; /SLAC; Plettner, Tomas; Byer, Robert L.; /Stanford U.

    2008-06-02

    We report the production of optically spaced attosecond microbunches produced by the inverse Free Electron Laser (IFEL) process. The IFEL is driven by a Ti:sapphire laser synchronized with the electron beam. The IFEL is followed by a magnetic chicane that converts the energy modulation into the longitudinal microbunch structure. The microbunch train is characterized by observing Coherent Optical Transition Radiation (COTR) at multiple harmonics of the bunching. The experimental results are compared with 1D analytic theory showing good agreement. Estimates of the bunching factors are given and correspond to a microbunch length of 350as fwhm. The formation of stable attosecond electron pulse trains marks an important step towards direct laser acceleration.

  6. Towards attosecond measurement in molecules and at surfaces

    Science.gov (United States)

    Marangos, Jonathan

    2015-05-01

    1) We will present a number of experimental approaches that are being developed at Imperial College to make attosecond timescale measurements of electronic dynamics in suddenly photoionized molecules and at surfaces. A brief overview will be given of some of the unanswered questions in ultrafast electron and hole dynamics in molecules and solids. These questions include the existence of electronic charge migration in molecules and how this process might couple to nuclear motion even on the few femtosecond timescale. How the timescale of photoemission from a surface may differ from that of an isolated atom, e.g. due to electron transport phenomena associated with the distance from the surface of the emitting atom and the electron dispersion relation, is also an open question. 2) The measurement techniques we are currently developing to answer these questions are HHG spectroscopy, attosecond pump-probe photoelectron/photoion studies, and attosecond pump-probe transient absorption as well as attosecond streaking for measuring surface emission. We will present recent advances in generating two synchronized isolated attosecond pulses at different colours for pump-probe measurements (at 20 eV and 90 eV respectively). Results on generation of isolated attosecond pulses at 300 eV and higher photon energy using a few-cycle 1800 nm OPG source will be presented. The use of these resources for making pump-probe measurements will be discussed. Finally we will present the results of streaking measurement of photoemission wavepackets from two types of surface (WO3 and a evaporated Au film) that show a temporal broadening of ~ 100 as compared to atomic streaks that is consistent with the electron mean free path in these materials. Work supported by ERC and EPSRC.

  7. Attosecond probing of state-resolved ionization and superpositions of atoms and molecules

    Science.gov (United States)

    Leone, Stephen

    2016-05-01

    Isolated attosecond pulses in the extreme ultraviolet are used to probe strong field ionization and to initiate electronic and vibrational superpositions in atoms and small molecules. Few-cycle 800 nm pulses produce strong-field ionization of Xe atoms, and the attosecond probe is used to measure the risetimes of the two spin orbit states of the ion on the 4d inner shell transitions to the 5p vacancies in the valence shell. Step-like features in the risetimes due to the subcycles of the 800 nm pulse are observed and compared with theory to elucidate the instantaneous and effective hole dynamics. Isolated attosecond pulses create massive superpositions of electronic states in Ar and nitrogen as well as vibrational superpositions among electronic states in nitrogen. An 800 nm pulse manipulates the superpositions, and specific subcycle interferences, level shifting, and quantum beats are imprinted onto the attosecond pulse as a function of time delay. Detailed outcomes are compared to theory for measurements of time-dynamic superpositions by attosecond transient absorption. Supported by DOE, NSF, ARO, AFOSR, and DARPA.

  8. Theory of attosecond absorption spectroscopy in krypton

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Lindroth, Eva; Madsen, Lars Bojer

    2012-01-01

    A theory for time-domain attosecond pump–attosecond probe photoabsorption spectroscopy is formulated and related to the atomic response. The theory is illustrated through a study of attosecond absorption spectroscopy in krypton. The atomic parameters entering the formulation such as energies and...... Auger widths, as well as wave functions and dipole coupling matrix elements, are determined by accurate many-body structure calculations. We create a hole in a valence shell by an attosecond pump, couple an inner-shell electron to the hole by an attosecond probe, and then monitor the formation of the...

  9. Absorption and emission of single attosecond light pulses in an autoionizing gaseous medium dressed by a time-delayed control field

    OpenAIRE

    Chu, Wei-Chun; C. D. Lin

    2012-01-01

    An extreme ultraviolet (EUV) single attosecond pulse passing through a laser-dressed dense gas is studied theoretically. The weak EUV pulse pumps the helium gas from the ground state to the 2s2p(1P) autoionizing state, which is coupled to the 2s2(1S) autoionizing state by a femtosecond infrared laser with the intensity in the order of 10^{12} W/cm2. The simulation shows how the transient absorption and emission of the EUV are modified by the coupling laser. A simple analytical expression for ...

  10. 0.5 keV soft X-ray attosecond continua

    CERN Document Server

    Teichmann, S M; Cousin, S L; Hemmer, M; Biegert, J

    2016-01-01

    Attosecond light pulses in the extreme ultraviolet have drawn a great deal of attention due to their ability to interrogate electronic dynamics in real time. Nevertheless, to follow charge dynamics and excitations in materials, element selectivity is a prerequisite, which demands such pulses in the soft X-ray region, above 200 eV, to simultaneously cover several fundamental absorption edges of the constituents of the materials. Here, we experimentally demonstrate the exploitation of a transient phase matching regime to generate carrier envelope controlled soft X-ray supercontinua with pulse energies up to 2.9 +/- 0.1 pJ and a flux of (7.3 +/- 0.1)x10^7 photons/s across the entire water window and attosecond pulses with 13 as transform limit. Our results herald attosecond science at the fundamental absorption edges of matter by bridging the gap between ultrafast temporal resolution and element specific probing.

  11. Reconstruction of an excited-state molecular wave packet with attosecond transient absorption spectroscopy

    Science.gov (United States)

    Cheng, Yan; Chini, Michael; Wang, Xiaowei; González-Castrillo, Alberto; Palacios, Alicia; Argenti, Luca; Martín, Fernando; Chang, Zenghu

    2016-08-01

    Attosecond science promises to allow new forms of quantum control in which a broadband isolated attosecond pulse excites a molecular wave packet consisting of a coherent superposition of multiple excited electronic states. This electronic excitation triggers nuclear motion on the molecular manifold of potential energy surfaces and can result in permanent rearrangement of the constituent atoms. Here, we demonstrate attosecond transient absorption spectroscopy (ATAS) as a viable probe of the electronic and nuclear dynamics initiated in excited states of a neutral molecule by a broadband vacuum ultraviolet pulse. Owing to the high spectral and temporal resolution of ATAS, we are able to reconstruct the time evolution of a vibrational wave packet within the excited B'Σ1u+ electronic state of H2 via the laser-perturbed transient absorption spectrum.

  12. Theory of strong-field attosecond transient absorption

    Science.gov (United States)

    Wu, Mengxi; Chen, Shaohao; Camp, Seth; Schafer, Kenneth J.; Gaarde, Mette B.

    2016-03-01

    Attosecond transient absorption is one of the promising new techniques being developed to exploit the availability of sub-femtosecond extreme ultraviolet (XUV) pulses to study the dynamics of the electron on its natural time scale. The temporal resolution in a transient absorption setup comes from the control of the relative delay and coherence between pump and probe pulses, while the spectral resolution comes from the characteristic width of the features that are being probed. In this review we focus on transient absorption scenarios where an attosecond pulse of XUV radiation creates a broadband excitation that is subsequently probed by a few cycle infrared (IR) laser. Because the attosecond XUV pulses are locked to the IR field cycle, the exchange of energy in the laser-matter interaction can be studied with unprecedented precision. We focus on the transient absorption by helium atoms of XUV radiation around the first ionization threshold, where we can simultaneoulsy solve the time-dependent Schrödinger equation for the single atom response and the Maxwell wave equation for the collective response of the nonlinear medium. We use a time-domain method that allows us to treat on an equal footing all the different linear and nonlinear processes by which the medium can exchange energy with the fields. We present several simple models, based on a few-level system interacting with a strong IR field, to explain many of the novel features found in attosecond transient absorption spectrograms. These include the presence of light-induced states, which demonstrate the ability to probe the dressed states of the atom. We also present a time-domain interpretation of the resonant pulse propagation features that appear in absorption spectra in dense, macroscopic media. We close by reviewing several recent experimental results that can be explained in terms of the models we discuss. Our aim is to present a road map for understanding future attosecond transient absorption

  13. Decoherence in Attosecond Photoionization

    OpenAIRE

    Pabst, Stefan; Greenman, L.; Ho, P; Mazziotti, D.; Santra, Robin

    2011-01-01

    The creation of superpositions of hole states via single-photon ionization using attosecond extreme-ultraviolet pulses is studied with the time-dependent configuration interaction singles (TDCIS) method. Specifically, the degree of coherence between hole states in atomic xenon is investigated. We find that interchannel coupling not only affects the hole populations, it also enhances the entanglement between the photoelectron and the remaining ion, thereby reducing the coherence within the ion...

  14. Exploring single-photon ionization on the attosecond time scale

    International Nuclear Information System (INIS)

    One of the fundamental processes in nature is the photoelectric effect in which an electron is ripped away from its atom via the interaction with a photon. This process was long believed to be instantaneous but with the development of attosecond pulses (1 as 10−18 s) we can finally get an insight into its dynamic. Here we measure a delay in ionization time between two differently bound electrons. The outgoing electrons are created via ionization with a train of attosecond pulses and we probe their relative delay with a synchronized infrared laser. We demonstrate how this probe field influences the measured delays and show that this contribution can be estimated with a universal formula, which allows us to extract field free atomic data.

  15. Entangled valence electron-hole dynamics revealed by stimulated attosecond x-ray Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Healion, Daniel; Zhang, Yu; Biggs, Jason D.; Govind, Niranjan; Mukamel, Shaul

    2012-09-06

    We show that broadband x-ray pulses can create wavepackets of valence electrons and holes localized in the vicinity of a selected atom (nitrogen, oxygen or sulfur in cysteine) by resonant stimulated Raman scattering. The subsequent dynamics reveals highly correlated motions of entangled electrons and hole quasiparticles. This information goes beyond the time-dependent total charge density derived from x-ray diffraction.

  16. Route to One Atomic Unit of Time: Development of a Broadband Attosecond Streak Camera

    Science.gov (United States)

    Zhao, Kun; Zhang, Qi; Chini, Michael; Chang, Zenghu

    A new attosecond streak camera based on a three-meter-long magnetic-bottle time-of-flight electron spectrometer (MBES) is developed. The temporal resolution of the photoelectron detection system is measured to be better than 250 ps, which is sufficient to achieve an energy resolution of 0.5 eV at 150 eV photoelectron energy. In preliminary experiments, a 94-as isolated XUV pulse was generated and characterized. With a new algorithm to retrieve the amplitude and phase of XUV pulses (PROOF—phase retrieval by omega oscillation filtering), the attosecond streak camera will be able to characterize isolated attosecond pulses as short as one atomic unit of time (25 as).

  17. Theoretical exploration of harmonic emission and attosecond pulse generation from H2+ in the presence of terahertz pulse

    Science.gov (United States)

    Liu, Hang; Feng, Liqiang

    2016-06-01

    Harmonic generation spectra from H2+ molecule ion driven by the chirped pulse combined with a terahertz (THz) pulse have been theoretically investigated by numerically solving the non-Born-Oppenheimer time-dependent Schrödinger equation (NBO-TDSE). The results show that with the introduction of the chirp, the harmonic cutoff is extended, resulting in a smooth supercontinuum. Further, when the initial vibrational state is prepared as v = 3, and by properly adding a THz controlling pulse, the harmonic yield is enhanced by almost six orders of magnitude compared with the single chirped pulse case. Quantum analyses are shown to explain the harmonic extension and enhancement. Furthermore, through the investigation of the isotopic effect, we find that more intense harmonics are generated in the lighter nucleus. Finally, by properly superposing the harmonics, a series of intense 35 as XUV pulses can be obtained, which are almost six orders of magnitude improvement in comparison with the single chirped pulse case.

  18. Generation of intense circularly polarized attosecond light bursts from relativistic laser plasmas

    CERN Document Server

    Ma, Guangjin; Yu, M Y; Shen, Baifei; Veisz, Laszlo

    2016-01-01

    We have investigated the polarization of attosecond light bursts generated by nanobunches of electrons from relativistic few-cycle laser pulse interaction with the surface of overdense plasmas. Particle-in-cell simulation shows that the polarization state of the generated attosecond burst depends on the incident-pulse polarization, duration, carrier envelope phase, as well as the plasma scale length. Through laser and plasma parameter control, without compromise of generation efficiency, a linearly polarized laser pulse with azimuth $\\theta^i=10^\\circ$ can generate an elliptically polarized attosecond burst with azimuth $|\\theta^r_{\\rm atto}|\\approx61^\\circ$ and ellipticity $\\sigma^r_{\\rm atto}\\approx0.27$; while an elliptically polarized laser pulse with $\\sigma^i\\approx0.36$ can generate an almost circularly polarized attosecond burst with $\\sigma^r_{\\rm atto}\\approx0.95$. The results propose a new way to a table-top circularly polarized XUV source as a probe with attosecond scale time resolution for many a...

  19. 高能阿秒脉冲聚焦及光谱分析复合系统设计%Design of a combined system for focusing and spectrum-analyzing of high energy attosecond pulse

    Institute of Scientific and Technical Information of China (English)

    王超; 王兴; 田进寿; 卢裕; 曹希斌; 王俊锋; 徐向晏; 温文龙

    2014-01-01

    为了减小阿秒脉冲聚焦反射过程的能量损失、降低阿秒脉冲测量过程中由聚焦像差引起的测量误差以及提高阿秒光脉冲光谱分析监测的可操作性,采用各环节性能分别优化的方法,设计了一种高能阿秒光脉冲聚焦及光谱分析复合系统,聚焦及光谱分析元件分别采用镀金掠入射型超环面镜和掠入射型凹面聚焦光栅,并给出了其具体结构和特性参量。结果表明,此系统适用于以短脉宽、高能量阿秒脉冲为新型探针的阿秒光谱学研究。%For reducing attosecond pulses energy loss in the focusing reflection process and measurement error caused by attosecond pulse focusing aberration measurement , as well as improving the operability of attosecond pulse spectroscopy monitoring , a combined focusing and spectrum-analysis system for attosecond pulse was designed through step-by-step performance optimization .The structure and characteristic parameters were given in detail .The focusing and spectrum-analyzing components are gold-coated grazing incidence toroidal mirror and grazing incidence concave focusing grating , respectively.The proposed system can find application in research platform of attosecond spectroscopy using high energy short attosecond pulse as basic probe tool .

  20. Quantum Chemistry on the time axis: electron correlations and rearrangements on femtosecond and attosecond scales

    CERN Document Server

    Nicolaides, Cleanthes A

    2015-01-01

    Recent developments toward the production and laboratory use of pulses of high intensity, and/or of very high frequency, and/or of ultrashort duration, make possible experiments which can produce time-resolved data on ultrafast transformations involving motions of electrons. The formulation, quantitative understanding and prediction of related new phenomena entail the possibility of computing and applying solutions of the many-electron time-dependent Schroedinger equation, for arbitrary electronic structures, including the dominant effects of Rydberg series, of multiply excited states and of the multi-channel continuous spectrum. To this purpose, we have proposed and applied to many prototypical cases the state-specific expansion approach (SSEA). (Mercouris, Komninos and Nicolaides, Adv. Quantum Chem. 60, 333 (2010)). The paper explains briefly the SSEA, and outlines four of its applications to recently formulated problems concerning time-resolved electronic processes, where electron correlations are crucial....

  1. Attosecond electronic and nuclear quantum photodynamics of ozone monitored with time and angle resolved photoelectron spectra

    CERN Document Server

    Decleva, P; Perveaux, A; Lauvergnat, D; Gatti, F; Lasorne, B; Halász, G J; Vibók, Á

    2016-01-01

    Recently we reported a series of numerical simulations proving that it is possible in principle to create an electronic wave packet and subsequent electronic motion in a neutral molecule photoexcited by a UV pump pulse within a few femtoseconds. We considered the ozone molecule: for this system the electronic wave packet leads to a dissociation process. In the present work, we investigate more specifically the time-resolved photoelectron angular distribution of the ozone molecule that provides a much more detailed description of the evolution of the electronic wave packet. We thus show that this experimental technique should be able to give access to observing in real time the creation of an electronic wave packet in a neutral molecule and its impact on a chemical process.

  2. 极紫外阿秒脉冲产生过程的本征原子相位分析%Analysis of intrinsic atomic phase in process of extreme ultraviolet attosecond pulse generation

    Institute of Scientific and Technical Information of China (English)

    王超; 刘虎林; 田进寿; 徐向晏; 曹希斌; 温文龙; 王俊锋

    2012-01-01

    In order to analyze the phase matching of extreme ultraviolet high harmonics in the process of attosecond pulses generation, the analytic expressions were achieved based on the three-step analysis model for optical field ionization high-harmonic generation (HHG) , and the harmonic spectral phase in the process of altosecund pulse generation was analyzed. It was found that, except the highest order harmonic, the spectral phase contribution of each harmonic consists of two sources of long trajectory electrons and short ones, and that, unlike the generated harmonics by the former, the spectral phase of those harmonics from the latter has regular phase relation among each other. The final conclusion is drawn that supprebsing the long trajectory electrons can reduce the pulse width of attosecond pulses, which is of great significance to the issue of high harmonic phase matching in generation of allosecond pulses.%为了研究高次谐波极紫外阿秒脉冲产生过程中的谐波相位匹配问题,基于光场电离高次谐波产生过程3步分析模型得出了高次谐波产生过程的理论描述解析式,并以此分析了阿秒脉冲产生过程中的高次谐波本征原子相位.由研究可知,除最高阶谐波外,对同一阶高次谐波产生有贡献的电子均有两类——长轨迹电子和短轨迹电子,各高次谐波长轨迹电子产生的谐波谱相之间几乎不存在线性关系,而短轨迹电子产生的高次谐波谱相之间则存在着良好的线性关系.结果表明,抑制各谐波长轨迹电子有助于产生更小脉宽阿秒脉冲.此结果对极紫外阿秒脉冲产生实验中的高次谐波相位匹配有重要的参考价值.

  3. Absence of Charge-Resonance-Enhanced Ionization in Attosecond Pulse Photoionization: Numerical Result on One-Dimensional H2+

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhe; ZHANG Gui-Zhong; XIANG Wang-Kua; W. T. Hill

    2006-01-01

    We present a numerical result of photoionization rate for the one-dimensional molecular hydrogen ion model exposed to intense light of 1×1016-2×1016 W/cm2, 55-as pulse duration, and 800nm wavelength. In contrast to the previous calculation result of charge-resonance-enhanced ionization for lower intensity and much longer pulse, our result exhibits an ionization saturation. The numerical results are interpreted in the field-dressed potential picture as over-the-barrier liberation of electrons. This extremely short pulsewidth and relatively high field phenomenon requests experimental demonstration.

  4. Monitoring conical intersections in the ring opening of furan by attosecond stimulated X-ray Raman spectroscopy

    Directory of Open Access Journals (Sweden)

    Weijie Hua

    2016-03-01

    Full Text Available Attosecond X-ray pulses are short enough to capture snapshots of molecules undergoing nonadiabatic electron and nuclear dynamics at conical intersections (CoIns. We show that a stimulated Raman probe induced by a combination of an attosecond and a femtosecond pulse has a unique temporal and spectral resolution for probing the nonadiabatic dynamics and detecting the ultrafast (∼4.5 fs passage through a CoIn. This is demonstrated by a multiconfigurational self-consistent-field study of the dynamics and spectroscopy of the furan ring-opening reaction. Trajectories generated by surface hopping simulations were used to predict Attosecond Stimulated X-ray Raman Spectroscopy signals at reactant and product structures as well as representative snapshots along the conical intersection seam. The signals are highly sensitive to the changes in nonadiabatically coupled electronic structure and geometry.

  5. Nonlinear reflection of high-amplitude laser pulses from relativistic electron mirrors

    Science.gov (United States)

    Kulagin, V. V.; Kornienko, V. N.; Cherepenin, V. A.

    2016-04-01

    A coherent X-ray pulse of attosecond duration can be formed in the reflection of a counterpropagating laser pulse from a relativistic electron mirror. The reflection of a high-amplitude laser pulse from the relativistic electron mirror located in the field of an accelerating laser pulse is investigated by means of two-dimensional (2D) numerical simulation. It is shown that provided the amplitude of the counterpropagating laser pulse is several times greater than the amplitude of the accelerating laser pulse, the reflection process is highly nonlinear, which causes a significant change in the X-ray pulse shape and its shortening up to generation of quasi-unipolar pulses and single-cycle pulses. A physical mechanism responsible for this nonlinearity of the reflection process is explained, and the parameters of the reflected X-ray pulses are determined. It is shown that the duration of these pulses may constitute 50 - 60 as, while their amplitude may be sub-relativistic.

  6. Attosecond clocking of scattering dynamics in dielectrics

    Science.gov (United States)

    Kling, Matthias

    2016-05-01

    In the past few years electronic-device scaling has progressed rapidly and miniaturization has reached physical gate lengths below 100 nm, heralding the age of nanoelectronics. Besides the effort in size scaling of integrated circuits, tremendous progress has recently been made in increasing the switching speed where strong-field-based ``dielectric-electronics'' may push it towards the petahertz frontier. In this contest, the investigation of the electronic collisional dynamics occurring in a dielectric material is of primary importance to fully understand the transport properties of such future devices. Here, we demonstrate attosecond chronoscopy of electron collisions in SiO2. In our experiment, a stream of isolated aerodynamically focused SiO2 nanoparticles of 50 nm diameter was delivered into the laser interaction region. Photoemission is initiated by an isolated 250 as pulse at 35 eV and the electron dynamics is traced by attosecond streaking using a delayed few-cycle laser pulse at 700 nm. Electrons were detected by a kilohertz, single-shot velocity-map imaging spectrometer, permitting to separate frames containing nanoparticle signals from frames containing the response of the reference gas only. We find that the nanoparticle photoemission exhibits a positive temporal shift with respect to the reference. In order to understand the physical origin of the shift we performed semi-classical Monte-Carlo trajectory simulations taking into account the near-field distributions in- and outside the nanoparticles as obtained from Mie theory. The simulations indicate a pronounced dependence of the streaking time shift near the highest measured electron energies on the inelastic scattering time, while elastic scattering only shows a small influence on the streaking time shift for typical dielectric materials. We envision our approach to provide direct time-domain access to inelastic scattering for a wide range of dielectrics.

  7. Ticking terahertz wave generation in attoseconds

    CERN Document Server

    Zhang, Dongwen; Meng, Chao; Du, Xiyu; Zhou, Zhaoyan; Zhao, Zengxiu; Yuan, Jianmin

    2012-01-01

    We perform a joint measurement of terahertz waves and high-order harmonics generated from noble atoms driven by a fundamental laser pulse and its second harmonic. By correlating their dependence on the phase-delay of the two pulses, we determine the generation of THz waves in tens of attoseconds precision. Compared with simulations and models, we find that the laser-assisted soft-collision of the electron wave packet with the atomic core plays a key role. It is demonstrated that the rescattering process, being indispensable in HHG processes, dominant THz wave generation as well but in a more elaborate way. The new finding might be helpful for the full characterization of the rescattering dynamics.

  8. Decoherence in attosecond photoionization.

    Science.gov (United States)

    Pabst, Stefan; Greenman, Loren; Ho, Phay J; Mazziotti, David A; Santra, Robin

    2011-02-01

    The creation of superpositions of hole states via single-photon ionization using attosecond extreme-ultraviolet pulses is studied with the time-dependent configuration-interaction singles (TDCIS) method. Specifically, the degree of coherence between hole states in atomic xenon is investigated. We find that interchannel coupling not only affects the hole populations, but it also enhances the entanglement between the photoelectron and the remaining ion, thereby reducing the coherence within the ion. As a consequence, even if the spectral bandwidth of the ionizing pulse exceeds the energy splittings among the hole states involved, perfectly coherent hole wave packets cannot be formed. For sufficiently large spectral bandwidth, the coherence can only be increased by increasing the mean photon energy. PMID:21405393

  9. Semiclassical model for attosecond angular streaking.

    Science.gov (United States)

    Smolarski, M; Eckle, P; Keller, U; Dörner, R

    2010-08-16

    Attosecond angular streaking is a new technique to achieve unsurpassed time accuracy of only a few attoseconds. Recently this has been successfully used to set an upper limit on the electron tunneling delay time in strong laser field ionization. The measurement technique can be modeled with either the time-dependent Schrödinger equation (TDSE) or a more simple semiclassical approach that describes the process in two steps in analogy to the three-step model in high harmonic generation (HHG): step one is the tunnel ionization and step two is the classical motion in the strong laser field. Here we describe in detail a semiclassical model which is based on the ADK theory for the tunneling step, with subsequent classical propagation of the electron in the laser field. We take into account different ellipticities of the laser field and a possible wavelength-dependent ellipticity that is typically observed for pulses in the two-optical-cycle regime. This semiclassical model shows excellent agreement with the experimental result. PMID:20721150

  10. Analysis of interference in attosecond transient absorption in adiabatic condition

    CERN Document Server

    Dong, Wenpu; Wang, Xiaowei; Zhao, Zengxiu

    2015-01-01

    We simulate the transient absorption of attosecond pulses of infrared laser-dressed atoms by considering a three-level system with the adiabatic approximation. We study the delay-dependent interference features in the transient absorption spectra of helium atoms from the perspective of the coherent interaction processes between the attosecond pulse and the quasi-harmonics, and find that many features of the interference fringes in the absorption spectra of the attosecond pulse can be attributed to the coherence phase difference. And the modulation signals of laser-induced sidebands of the dark state is found related to the dark state with population modulated by the dressing field.

  11. Attosecond strong-field interferometry in graphene: Chirality, singularity, and Berry phase

    Science.gov (United States)

    Kelardeh, Hamed Koochaki; Apalkov, Vadym; Stockman, Mark I.

    2016-04-01

    We propose an interferometry in graphene's reciprocal space without a magnetic field, employing strong ultrafast circularly polarized optical pulses. The reciprocal space interferograms contain information on the electronic spectra and topological properties of graphene and on the waveform and circular polarization of the excitation optical pulses. These can be measured using angle-resolved photoemission spectroscopy (ARPES) with attosecond ultraviolet pulses. The predicted effects provide unique opportunities in fundamental studies of two-dimensional topological materials and in applications to future petahertz light-wave-driven electronics.

  12. Time-resolved photoemission using attosecond streaking

    CERN Document Server

    Nagele, Stefan; Wais, Michael; Wachter, Georg; Burgdörfer, Joachim

    2014-01-01

    We theoretically study time-resolved photoemission in atoms as probed by attosecond streaking. We review recent advances in the study of the photoelectric effect in the time domain and show that the experimentally accessible time shifts can be decomposed into distinct contributions that stem from the field-free photoionization process itself and from probe-field induced corrections. We perform accurate quantum-mechanical as well as classical simulations of attosecond streaking for effective one-electron systems and determine all relevant contributions to the time delay with attosecond precision. In particular, we investigate the properties and limitations of attosecond streaking for the transition from short-ranged potentials (photodetachment) to long-ranged Coulomb potentials (photoionization). As an example for a more complex system, we study time-resolved photoionization for endohedral fullerenes $A$@$\\text{C}_{60}$ and discuss how streaking time shifts are modified due to the interaction of the $\\text{C}_...

  13. Probing single-photon ionization on the attosecond time scale

    CERN Document Server

    Klünder, K; Gisselbrecht, M; Fordell, T; Swoboda, M; Guénot, D; Johnsson, P; Caillat, J; Mauritsson, J; Maquet, A; Taïeb, R; L'Huillier, A

    2010-01-01

    We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the $3s^2$ and from the $3p^6$ shell, at different excitation energies ranging from 32 to 42 eV. The determination of single photoemission time delays requires to take into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using an universal formula and is found to account for a substantial fraction of the measured delay.

  14. Conservation laws, bilinear forms and solitons for a fifth-order nonlinear Schrödinger equation for the attosecond pulses in an optical fiber

    International Nuclear Information System (INIS)

    Under investigation in this paper is a fifth-order nonlinear Schrödinger equation, which describes the propagation of attosecond pulses in an optical fiber. Based on the Lax pair, infinitely-many conservation laws are derived. With the aid of auxiliary functions, bilinear forms, one-, two- and three-soliton solutions in analytic forms are generated via the Hirota method and symbolic computation. Soliton velocity varies linearly with the coefficients of the high-order terms. Head-on interaction between the bidirectional two solitons and overtaking interaction between the unidirectional two solitons as well as the bound state are depicted. For the interactions among the three solitons, two head-on and one overtaking interactions, three overtaking interactions, an interaction between a bound state and a single soliton and the bound state are displayed. Graphical analysis shows that the interactions between the two solitons are elastic, and interactions among the three solitons are pairwise elastic. Stability analysis yields the modulation instability condition for the soliton solutions

  15. Conservation laws, bilinear forms and solitons for a fifth-order nonlinear Schrödinger equation for the attosecond pulses in an optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Chai, Jun; Tian, Bo, E-mail: tian_bupt@163.com; Zhen, Hui-Ling; Sun, Wen-Rong

    2015-08-15

    Under investigation in this paper is a fifth-order nonlinear Schrödinger equation, which describes the propagation of attosecond pulses in an optical fiber. Based on the Lax pair, infinitely-many conservation laws are derived. With the aid of auxiliary functions, bilinear forms, one-, two- and three-soliton solutions in analytic forms are generated via the Hirota method and symbolic computation. Soliton velocity varies linearly with the coefficients of the high-order terms. Head-on interaction between the bidirectional two solitons and overtaking interaction between the unidirectional two solitons as well as the bound state are depicted. For the interactions among the three solitons, two head-on and one overtaking interactions, three overtaking interactions, an interaction between a bound state and a single soliton and the bound state are displayed. Graphical analysis shows that the interactions between the two solitons are elastic, and interactions among the three solitons are pairwise elastic. Stability analysis yields the modulation instability condition for the soliton solutions.

  16. Observation of molecular dipole excitations by attosecond self-streaking

    CERN Document Server

    Wachter, Georg; Sato, Shunsuke A; Pazourek, Renate; Wais, Michael; Lemell, Christoph; Tong, Xiao-Min; Yabana, Kazuhiro; Burgdörfer, Joachim

    2015-01-01

    We propose a protocol to probe the ultrafast evolution and dephasing of coherent electronic excitation in molecules in the time domain by the intrinsic streaking field generated by the molecule itself. Coherent electronic motion in the endohedral fullerene \\Necsixty~is initiated by a moderately intense femtosecond UV-VIS pulse leading to coherent oscillations of the molecular dipole moment that persist after the end of the laser pulse. The resulting time-dependent molecular near-field is probed through the momentum modulation of photoemission from the central neon atom by a time-delayed attosecond XUV pulse. Our ab-initio time-dependent density functional theory and classical trajectory simulations predict that this self-streaking signal accurately traces the molecular dipole oscillations in real time. We discuss the underlying processes and give an analytical model that captures the essence of our ab-initio simulations.

  17. Ultrashort and coherent single-electron pulses for diffraction at ultimate resolutions

    International Nuclear Information System (INIS)

    energies of tens of keV which extends the attosecond streaking methodology to freely propagating electrons. We study the laser streaking effect in detail both experimentally and by numerical simulations and reveal its potential for characterizing electron pulses with durations down to the sub-femtosecond regime. In addition, the method enables the determination of the energy bandwidth and the chirp of the electrons. Finally, we developed a microspectrometer for the characterization of samples for ultrafast electron diffraction. These samples have a typical thickness of tens of nanometers and are often only a few hundred micrometers in diameter.

  18. Attosecond electronic and nuclear quantum photodynamics of ozone: time-dependent Dyson orbitals and dipole

    CERN Document Server

    Perveaux, A; Lasorne, B; Gatti, F; Robb, M A; Halász, G J; Vibók, Á

    2014-01-01

    A nonadiabatic scheme for the description of the coupled electron and nuclear motions in the ozone molecule was proposed recently. An initial coherent nonstationary state was prepared as a superposition of the ground state and the excited Hartley band. In this situation neither the electrons nor the nuclei are in a stationary state. The multiconfiguration time dependent Hartree method was used to solve the coupled nuclear quantum dynamics in the framework of the adiabatic separation of the time-dependent Schr\\"odinger equation. The resulting wave packet shows an oscillation of the electron density between the two chemical bonds. As a first step for probing the electronic motion we computed the time-dependent molecular dipole and the Dyson orbitals. The latter play an important role in the explanation of the photoelectron angular distribution. Calculations of the Dyson orbitals are presented both for the time-independent as well as the time-dependent situations. We limited our description of the electronic mot...

  19. Intensity Dependence of Laser-Assisted Attosecond Photoionization Spectra

    CERN Document Server

    Swoboda, M; Ruchon, T; Johnsson, P; Mauritsson, J; Schafer, K J; L'Huillier, A

    2009-01-01

    We study experimentally the influence of the intensity of the infrared (IR) probe field on attosecond pulse train (APT) phase measurements performed with the RABITT method (Reconstruction of Attosecond Beating by Interference in Two-Photon Transitions). We find that if a strong IR field is applied, the attosecond pulses will appear to have lower-than-actual chirp rates. We also observe the onset of the streaking regime in the breakdown of the weak-field RABITT conditions. We perform a Fourier-analysis of harmonic and sideband continuum states and show that the mutual phase relation of the harmonics can be extracted from higher Fourier components.

  20. Attosecond time delays in the nuclear dynamics of strong-field molecular dissociation

    Science.gov (United States)

    Armstrong, Greg; Ultrafast Molecular Physics Group Collaboration

    2016-05-01

    The relative time delay in the photoemission from neighboring atomic valence sub-shells has become an area of considerable recent interest, with delays of tens of attoseconds reported in pump-probe experiments for a number of atomic targets. Such delays may be extracted, for example, from phase differences in the photoelectron energy spectra for the different sub-shells as a function of delay between pump and probe pulses. The focus of such experiments has, to date, been atomic targets, on the assumption that only electronic motion can lead to delays on the attosecond scale.We investigate the molecular analogue of such studies by calculating the kinetic-energy release (KER) spectrum for neighboring vibrational states as a function of pump-probe delay time. In particular, we focus on molecular targets where electronic excitation is negligible, and show that attosecond time delays are also possible for purely nuclear motion. We will present evidence of these attosecond delays derived from both numerical solutions of the time-dependent Schrödinger equation and experiment. We analyze and understand the observed shifts using the photon-phase formalism. G.S.J. Armstrong, J. McKenna, B. Gaire, M. Zohrabi, B. Berry, B. Jochim, Kanaka Raju, P., P. Feizollah, K.D. Carnes, Ben-Itzhak, B.D. Esry.

  1. Attosecond delays in molecular photoionization

    CERN Document Server

    Huppert, Martin; Baykusheva, Denitsa; von Conta, Aaron; Wörner, Hans Jakob

    2016-01-01

    We report measurements of energy-dependent attosecond photoionization delays between the two outer-most valence shells of N$_2$O and H$_2$O. The combination of single-shot signal referencing with the use of different metal foils to filter the attosecond pulse train enables us to extract delays from congested spectra. Remarkably large delays up to 160 as are observed in N$_2$O, whereas the delays in H$_2$O are all smaller than 50 as in the photon-energy range of 20-40 eV. These results are interpreted by developing a theory of molecular photoionization delays. The long delays measured in N$_2$O are shown to reflect the population of molecular shape resonances that trap the photoelectron for a duration of up to $\\sim$110 as. The unstructured continua of H$_2$O result in much smaller delays at the same photon energies. Our experimental and theoretical methods make the study of molecular attosecond photoionization dynamics accessible.

  2. 0.5-keV Soft X-ray attosecond continua.

    Science.gov (United States)

    Teichmann, S M; Silva, F; Cousin, S L; Hemmer, M; Biegert, J

    2016-01-01

    Attosecond light pulses in the extreme ultraviolet have drawn a great deal of attention due to their ability to interrogate electronic dynamics in real time. Nevertheless, to follow charge dynamics and excitations in materials, element selectivity is a prerequisite, which demands such pulses in the soft X-ray region, above 200 eV, to simultaneously cover several fundamental absorption edges of the constituents of the materials. Here, we experimentally demonstrate the exploitation of a transient phase matching regime to generate carrier envelope controlled soft X-ray supercontinua with pulse energies up to 2.9±0.1 pJ and a flux of (7.3±0.1) × 10(7) photons per second across the entire water window and attosecond pulses with 13 as transform limit. Our results herald attosecond science at the fundamental absorption edges of matter by bridging the gap between ultrafast temporal resolution and element specific probing. PMID:27167525

  3. Ionization and transient absorption control with a resonant attosecond clock

    International Nuclear Information System (INIS)

    Metastable states are important actors in the ionisation of atoms and molecules. Sub-femtosecond extreme ultraviolet pulses can coherently populate several transiently bound states at once, thus starting the attosecond clocks which are required to monitor and control ultrafast electronic evolution above the ionisation threshold. Here we illustrate, from a theoretical point of view, the effects coherent superpositions of 1Po doubly excited states in the helium atom have on channel-resolved photoelectron spectra as well as on the transient absorption spectrum of the atom in the extreme ultraviolet region, when they are created by a single-attosecond pulse in the presence of a strong few-cycle near-infrared/visible pulse which acts as a probe. Interference fringes varying rapidly with the pump-probe time delay are visible in both photoelectron and transient absorption spectra. From such fringes, the wave packet itself can conceivably be reconstructed. Conversely, all observables are modulated by the characteristic beating periods of the wave packet, so that control of partial ionisation yields, branching ratios, and light absorption or amplification can be achieved

  4. Communication: The electronic structure of matter probed with a single femtosecond hard x-ray pulse

    Directory of Open Access Journals (Sweden)

    J. Szlachetko

    2014-03-01

    Full Text Available Physical, biological, and chemical transformations are initiated by changes in the electronic configuration of the species involved. These electronic changes occur on the timescales of attoseconds (10−18 s to femtoseconds (10−15 s and drive all subsequent electronic reorganization as the system moves to a new equilibrium or quasi-equilibrium state. The ability to detect the dynamics of these electronic changes is crucial for understanding the potential energy surfaces upon which chemical and biological reactions take place. Here, we report on the determination of the electronic structure of matter using a single self-seeded femtosecond x-ray pulse from the Linac Coherent Light Source hard x-ray free electron laser. By measuring the high energy resolution off-resonant spectrum (HEROS, we were able to obtain information about the electronic density of states with a single femtosecond x-ray pulse. We show that the unoccupied electronic states of the scattering atom may be determined on a shot-to-shot basis and that the measured spectral shape is independent of the large intensity fluctuations of the incoming x-ray beam. Moreover, we demonstrate the chemical sensitivity and single-shot capability and limitations of HEROS, which enables the technique to track the electronic structural dynamics in matter on femtosecond time scales, making it an ideal probe technique for time-resolved X-ray experiments.

  5. Strong-field-induced attosecond dynamics in SiO2

    Directory of Open Access Journals (Sweden)

    Kienberger R.

    2013-03-01

    Full Text Available Striking field-induced changes in the absorption near the Si L-edge of SiO2 exposed to a near-infrared laser field of several V/Å delivered by a few-cycle pulse are observed with sub-100 attosecond extreme ultraviolet pulses by means of attosecond transient absorption.

  6. Synthesis and characterization of attosecond light vortices in the extreme ultraviolet

    Science.gov (United States)

    Géneaux, R.; Camper, A.; Auguste, T.; Gobert, O.; Caillat, J.; Taïeb, R.; Ruchon, T.

    2016-08-01

    Infrared and visible light beams carrying orbital angular momentum (OAM) are currently thoroughly studied for their extremely broad applicative prospects, among which are quantum information, micromachining and diagnostic tools. Here we extend these prospects, presenting a comprehensive study for the synthesis and full characterization of optical vortices carrying OAM in the extreme ultraviolet (XUV) domain. We confirm the upconversion rules of a femtosecond infrared helically phased beam into its high-order harmonics, showing that each harmonic order carries the total number of OAM units absorbed in the process up to very high orders (57). This allows us to synthesize and characterize helically shaped XUV trains of attosecond pulses. To demonstrate a typical use of these new XUV light beams, we show our ability to generate and control, through photoionization, attosecond electron beams carrying OAM. These breakthroughs pave the route for the study of a series of fundamental phenomena and the development of new ultrafast diagnosis tools using either photonic or electronic vortices.

  7. GENERATION OF ATTOSECOND PULSES FROM THE INTERACTION OF OBLIQUE INCIDENT LASER PULSE WITH OVERDENSE PLASMA p%斜入射激光脉冲与稠密等离子体相互作用产生的阿秒脉冲

    Institute of Scientific and Technical Information of China (English)

    罗牧华; 张秋菊

    2011-01-01

    Using one - dimensional particle - in - cell simulations, the generation of attosecond pulses is studied, which is obtained through the interaction of a short oblique incident laser pulse with overdense plasma. It is observed that the intensity and conversion efficiency of attosecond pulses at oblique incidence is always higher than the normal incidence at the same parameters. And the number of attosecond pulses for the oblique incident laser pulse is only one half of the normal incidence. According to the oscillating mirror model and the equation of the mirror motion, we analyze the reason of these questions. Furthermore, when the density of plasma is invariable and the intensity of the laser pulse is raised, with the increase the times of filtering, the conversion ratio of attosecond pulses for the oblique and normal incidence shows an approaching tendency. After selecting harmonics above the order of 300, then we can get the attosecond pulses that have reached the X - ray region.%利用一维粒子模拟程序研究和比较了斜入射和垂直入射激光脉冲与稠密等离子体相互作用得到的阿秒脉冲以及激光强度对阿秒脉冲转换比率的影响.同样参数下,斜入射的阿秒脉冲转换比率明显高于垂直入射的情况,滤波后得到的阿秒脉冲振幅比较大,而脉冲串中阿秒脉冲的个数则是垂直入射时的一半.根据振荡镜面模型对两种情况进行了分析,由镜面振荡方程可以对结果给出解释.保持等离子体密度不变,增大入射激光强度时,随着滤波次数的增加,斜入射与垂直入射的阿秒脉冲的转换比率逐渐趋于相同.300次以上高通滤波后我们得到了处于X射线范围的阿秒脉冲.

  8. A new technique to generate 100 GW-level attosecond X-ray pulses from the X-ray SASE FELs

    CERN Document Server

    Saldin, E L; Yurkov, M V

    2004-01-01

    We propose a scheme for generation of single 100 GW 300-as pulse in the X-ray free electron laser with the use of a few cycles optical pulse from Ti:sapphire laser system. Femtosecond optical pulse interacts with the electron beam in the two-period undulator resonant to 800 nm wavelength and produces energy modulation within a slice of the electron bunch. Following the energy modulator the electron beam enters the first part of the baseline gap-adjustable X-ray undulator and produces SASE radiation with 100 MW-level power. Due to energy modulation the frequency is correlated to the longitudinal position within the few-cycle-driven slice of the SASE radiation pulse. The largest frequency offset corresponds to a single-spike pulse in the time domain which is confined to one half-oscillation period near the central peak electron energy. After the first undulator the electron beam is guided through a magnetic delay which we use to position the X-ray spike with the largest frequency offset at the "fresh" part of t...

  9. Attosecond nanoscale near-field sampling

    CERN Document Server

    Förg, Benjamin; Suessmann, Frederik; Foerster, Michael; Krueger, Michael; Ahn, Byung-Nam; Wintersperger, Karen; Zherebtsov, Sergey; Guggenmos, Alexander; Pervak, Vladimir; Kessel, Alexander; Trushin, Sergei; Azzeer, Abdallah; Stockman, Mark; Kim, Dong-Eon; Krausz, Ferenc; Hommelhoff, Peter; Kling, Matthias

    2015-01-01

    The promise of ultrafast light field driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical nearfields from light interaction with nanostructures with sub cycle resolution. Here, we experimentally demonstrate attosecond nearfield retrieval with a gold nanotip using streaking spectroscopy. By comparison of the results from gold nanotips to those obtained for a noble gas, the spectral response of the nanotip near field arising from laser excitation can be extracted. Monte Carlo MC trajectory simulations in near fields obtained with the macroscopic Maxwells equations elucidate the streaking mechanism on the nanoscale.

  10. Attosecond nanoscale near-field sampling

    Science.gov (United States)

    Förg, B.; Schötz, J.; Süßmann, F.; Förster, M.; Krüger, M.; Ahn, B.; Okell, W. A.; Wintersperger, K.; Zherebtsov, S.; Guggenmos, A.; Pervak, V.; Kessel, A.; Trushin, S. A.; Azzeer, A. M.; Stockman, M. I.; Kim, D.; Krausz, F.; Hommelhoff, P.; Kling, M. F.

    2016-01-01

    The promise of ultrafast light-field-driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical near fields from light interaction with nanostructures, with sub-cycle resolution. Here we experimentally demonstrate attosecond near-field retrieval for a tapered gold nanowire. By comparison of the results to those obtained from noble gas experiments and trajectory simulations, the spectral response of the nanotaper near field arising from laser excitation can be extracted. PMID:27241851

  11. Attosecond dynamical Franz-Keldysh effect in polycrystalline diamond.

    Science.gov (United States)

    Lucchini, M; Sato, S A; Ludwig, A; Herrmann, J; Volkov, M; Kasmi, L; Shinohara, Y; Yabana, K; Gallmann, L; Keller, U

    2016-08-26

    Short, intense laser pulses can be used to access the transition regime between classical and quantum optical responses in dielectrics. In this regime, the relative roles of inter- and intraband light-driven electronic transitions remain uncertain. We applied attosecond transient absorption spectroscopy to investigate the interaction between polycrystalline diamond and a few-femtosecond infrared pulse with intensity below the critical intensity of optical breakdown. Ab initio time-dependent density functional theory calculations, in tandem with a two-band parabolic model, accounted for the experimental results in the framework of the dynamical Franz-Keldysh effect and identified infrared induction of intraband currents as the main physical mechanism responsible for the observations. PMID:27563093

  12. 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

  13. Coherent excitation with short electron pulses

    Science.gov (United States)

    Guertler, Andreas; Robicheaux, Francis; Noordam, Bart

    2000-06-01

    [1pt] The probability for a transition within an atom to be driven by a collision with a long pulse of electrons is proportional to the electron flux with the proportionality factor being the cross section for this transition. Recently it was shown [1] that for electron pulses shorter than the orbit time of the electron in the atom, a contribution of coherent scattering plays a role, which is proportional to the differential cross section in forward direction and the square of the electron flux. To investigate this effect, we are developing a picosecond electron gun [2]. Collision experiments will be done with Rydberg states in lithium around n=40 with Kepler orbit times in the order of 10 ps. For picosecond electron pulses, a quadratic dependance of the transition probability on the electron flux is expected in contrast to the linear dependance expected for nanosecond electron pulses. [1pt] References [1pt] [1] F. Robicheaux and L. D. Noordam, submitted to Phys. Rev. Lett. [1pt] [2] F. Robicheaux, G. M. Lankhuijzen, and L. D. Noordam, JOSA B 15, 1 (1998)

  14. π-Electron rotations in chiral aromatic molecules induced by ultashort laser pulses

    International Nuclear Information System (INIS)

    π Electron play an important role in formation of the molecular structures and reactivity of aromatic molecules. In recent years, research fields of electron dynamics in atoms and molecules have attracted considerable attention with rapid progress in laser science and technology in femtosecond to attosecond time regimes [1]. This is a new branch of femtosecond chemistry. In this talk, we present the results of our recent works on control of π-electron rotation in photo-induced chiral aromatic molecules [2-4]. Control of π-electron rotation has potential utility to next-generation ultrafast switching devices. After a short introduction, the principle of generation of unidirectional π-electron rotation in aromatic molecules induced by a linearly polarized UV laser pulse is described. Next, the results of control simulations of π-electron rotations and those of the π- electron ring currents are presented for two representative chiral aromatic molecules; one is 2,5-dichlor[n] (3,6) pyrazinophane with one aromatic pyrzine ring [2], and the other is (P)-2,2’-biphenol with two aromatic rings [3,4]. Finally, the summary of the π-electron rotations and perspectives of ultrashort quantum switching investigations are described. (author)

  15. Electron photodetachment by short laser pulse

    NARCIS (Netherlands)

    Golovinski, P. A.; Drobyshev, A. A.

    2012-01-01

    Expressions are derived for calculations of the total probabilities and electron spectra for the photodetachment of electrons from negative ions with filled valence s shells by ultrashort laser pulses. Particular calculations have been performed for two negative ions (H- and Li-) and titanium-sapphi

  16. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, I.; Huppert, M.; Wörner, H. J., E-mail: hwoerner@ethz.ch [Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich (Switzerland); Brown, M. A. [Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich (Switzerland); Bokhoven, J. A. van [Institute for Chemical and Bioengineering, ETH Zurich, Vladimir-Prelog-Weg 1, 8093 Zurich (Switzerland); Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institute, 5232 Villigen (Switzerland)

    2015-12-15

    A new apparatus for attosecond time-resolved photoelectron spectroscopy of liquids and gases is described. It combines a liquid microjet source with a magnetic-bottle photoelectron spectrometer and an actively stabilized attosecond beamline. The photoelectron spectrometer permits venting and pumping of the interaction chamber without affecting the low pressure in the flight tube. This pressure separation has been realized through a sliding skimmer plate, which effectively seals the flight tube in its closed position and functions as a differential pumping stage in its open position. A high-harmonic photon spectrometer, attached to the photoelectron spectrometer, exit port is used to acquire photon spectra for calibration purposes. Attosecond pulse trains have been used to record photoelectron spectra of noble gases, water in the gas and liquid states as well as solvated species. RABBIT scans demonstrate the attosecond resolution of this setup.

  17. Light field driven streak-camera for single-shot measurements of the temporal profile of XUV-pulses from a free-electron laser; Lichtfeld getriebene Streak-Kamera zur Einzelschuss Zeitstrukturmessung der XUV-Pulse eines Freie-Elektronen Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Fruehling, Ulrike

    2009-10-15

    The Free Electron Laser in Hamburg (FLASH) is a source for highly intense ultra short extreme ultraviolet (XUV) light pulses with pulse durations of a few femtoseconds. Due to the stochastic nature of the light generation scheme based on self amplified spontaneous emission (SASE), the duration and temporal profile of the XUV pulses fluctuate from shot to shot. In this thesis, a THz-field driven streak-camera capable of single pulse measurements of the XUV pulse-profile has been realized. In a first XUV-THz pump-probe experiment at FLASH, the XUV-pulses are overlapped in a gas target with synchronized THz-pulses generated by a new THz-undulator. The electromagnetic field of the THz light accelerates photoelectrons produced by the XUV-pulses with the resulting change of the photoelectron momenta depending on the phase of the THz field at the time of ionisation. This technique is intensively used in attosecond metrology where near infrared streaking fields are employed for the temporal characterisation of attosecond XUV-Pulses. Here, it is adapted for the analysis of pulse durations in the few femtosecond range by choosing a hundred times longer far infrared streaking wavelengths. Thus, the gap between conventional streak cameras with typical resolutions of hundreds of femtoseconds and techniques with attosecond resolution is filled. Using the THz-streak camera, the time dependent electric field of the THz-pulses was sampled in great detail while on the other hand the duration and even details of the time structure of the XUV-pulses were characterized. (orig.)

  18. Attosecond Delays in Molecular Photoionization

    Science.gov (United States)

    Huppert, Martin; Jordan, Inga; Baykusheva, Denitsa; von Conta, Aaron; Wörner, Hans Jakob

    2016-08-01

    We report measurements of energy-dependent photoionization delays between the two outermost valence shells of N2O and H2O . The combination of single-shot signal referencing with the use of different metal foils to filter the attosecond pulse train enables us to extract delays from congested spectra. Remarkably large delays up to 160 as are observed in N2O , whereas the delays in H2O are all smaller than 50 as in the photon-energy range of 20-40 eV. These results are interpreted by developing a theory of molecular photoionization delays. The long delays measured in N2O are shown to reflect the population of molecular shape resonances that trap the photoelectron for a duration of up to ˜110 as. The unstructured continua of H2O result in much smaller delays at the same photon energies. Our experimental and theoretical methods make the study of molecular attosecond photoionization dynamics accessible.

  19. 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

  20. Attosecond control of dissociative ionization of O{sub 2} molecules

    Energy Technology Data Exchange (ETDEWEB)

    Siu, W.; Kelkensberg, F.; Gademann, G. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Rouzee, A.; Vrakking, M. J. J. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Max-Born-Institut, Max-Born Strasse 2A, D-12489 Berlin (Germany); Johnsson, P. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Department of Physics, Lund University, Post Office Box 118, SE-221 00 Lund (Sweden); Dowek, D. [Laboratoire des Collisions Atomiques et Moleculaires (UMR Universite Paris-Sud et CNRS, 8625), Batiment 351, Universite Paris-Sud, F-91405 Orsay Cedex (France); Lucchini, M.; Calegari, F. [Department of Physics, Politecnico di Milano, Istituto di Fotonica e Nanotecnologie CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); De Giovannini, U.; Rubio, A. [Nano-bio Spectroscopy Group, ETSF Scientific Development Centre, Universidad del Pais Vasco, Avenida Tolosa 72, E-20018 San Sebastian (Spain); Lucchese, R. R. [Department of Chemistry, Texas A and M University, Post Office Box 30012, College Station, Texas 77842-3012 (United States); Kono, H. [Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan); Lepine, F. [Universite Lyon 1/CNRS/LASIM, UMR 5579, 43 Boulevard Du 11 Novembre 1918, F-69622 Villeurbane (France)

    2011-12-15

    We demonstrate that dissociative ionization of O{sub 2} can be controlled by the relative delay between an attosecond pulse train (APT) and a copropagating infrared (IR) field. Our experiments reveal a dependence of both the branching ratios between a range of electronic states and the fragment angular distributions on the extreme ultraviolet (XUV) to IR time delay. The observations go beyond adiabatic propagation of dissociative wave packets on IR-induced quasistatic potential energy curves and are understood in terms of an IR-induced coupling between electronic states in the molecular ion.

  1. Correlation dynamics between electrons and ions in the fragmentation of D$_2$ molecules by short laser pulses

    CERN Document Server

    Tong, X M; Lin, C D

    2003-01-01

    We studied the recollision dynamics between the electrons and D$_2^+$ ions following the tunneling ionization of D$_2$ molecules in an intense short pulse laser field. The returning electron collisionally excites the D$_2^+$ ion to excited electronic states from there D$_2^+$ can dissociate or be further ionized by the laser field, resulting in D$^+$ + D or D$^+$ + D$^+$, respectively. We modeled the fragmentation dynamics and calculated the resulting kinetic energy spectrum of D$^+$ to compare with recent experiments. Since the recollision time is locked to the tunneling ionization time which occurs only within fraction of an optical cycle, the peaks in the D$^+$ kinetic energy spectra provides a measure of the time when the recollision occurs. This collision dynamics forms the basis of the molecular clock where the clock can be read with attosecond precision, as first proposed by Corkum and coworkers. By analyzing each of the elementary processes leading to the fragmentation quantitatively, we identified ho...

  2. Attosecond photoionization dynamics with stimulated core-valence transitions

    Science.gov (United States)

    You, Jhih-An; Rohringer, Nina; Dahlström, Jan Marcus

    2016-03-01

    We investigate ionization of neon atoms by an isolated attosecond pump pulse in the presence of two coherent extreme ultraviolet or x-ray probe fields. The probe fields are tuned to a core-valence transition in the residual ion and induce spectral shearing of the photoelectron distributions. We show that the photoelectron-ion coincidence signal contains an interference pattern that depends on the temporal structure of the attosecond pump pulse and the stimulated core-valence transition. Many-body perturbation theory is used to compute "atomic response times" for the processes and we find strikingly different behavior for stimulation to the outer-core hole (2 p ↔2 s ) and stimulation to the inner-core hole (2 p ↔1 s ). The response time of the inner-core transition is found to be comparable to that of state-of-the-art laser-based characterization techniques for attosecond pulses.

  3. Transient Impulsive Giant Electronic Raman Redistribution

    CERN Document Server

    Miyabe, S

    2014-01-01

    Resonant Raman excitation by ultrafast vacuum ultraviolet laser pulses is a powerful means to study electron dynamics in molecules, but experiments must contend with linear background ionization: frequencies high enough to reach resonant core-valence transitions will usually ionize all occupied orbitals as well, and the ionization cross sections are usually dominant. Here we show that attosecond pulses can induce a new process, transient impulsive stimulated Raman scattering, which can overwhelm valence ionization. Calculations are performed for atomic sodium, but the principal is valid for many molecular systems. This approach opens the path for high fidelity multidimensional spectroscopy with attosecond pulses.

  4. 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.

  5. On the Attosecond charge migration in Cl.....N, Cl.....O, Br.....N and Br.....O Halogen-bonded clusters: Effect of donor, acceptor, vibration, rotation, and electron correlation

    Indian Academy of Sciences (India)

    SANKHABRATA CHANDRA; MOHAMMED MUSTHAFA IQBAL; ATANU BHATTACHARYA

    2016-08-01

    The electron-electron relaxation and correlation-driven charge migration process, which features pure electronic aspect of ultrafast charge migration phenomenon, occurs on a very short timescale in ionized molecules and molecular clusters, prior to the onset of nuclear motion. In this article, we have presented natureof ultrafast pure electronic charge migration dynamics through Cl.....N, Cl.....O, Br.....N, and Br.....O halogen bonds, explored using density functional theory. We have explored the role of donor, acceptor, electron correlation, vibration and rotation in charge migration dynamics through these halogen bonds. For this work, we have selected ClF, Cl₂, ClOH, ClCN, BrF, BrCl, BrOH, and BrCN molecules paired with either NH₃ or H₂O. We have found that the timescale for pure electron-electron relaxation and correlation-driven charge migration through the Cl.....N, Br.....N, Cl.....O, and Br.....O halogen bonds falls in the range of 300–600 attosecond. The primary driving force behind the attosecond charge migration through the Cl.....N, Br.....N, Cl.....O, and Br.....O halogen bonds is the energy difference (∆E) between two stationary cationic orbitals (LUMO-β and HOMO-β), which together represents the initial hole density immediately following vertical ionization. We have also predicted that the strength of electron correlation has significant effect on the charge migration timescale in Cl.....N, Br.....N, Cl.....O, and Br.....O halogen bonded clusters. Vibration and rotation are also found to exhibit profound effect on attosecond charge migration dynamics through halogen bonds.

  6. Introduction to attosecond delays in photoionization

    International Nuclear Information System (INIS)

    This tutorial presents an introduction to the interaction of light and matter on the attosecond timescale. Our aim is to detail the theoretical description of ultra-short time delays and to relate these to the phase of extreme ultraviolet (XUV) light pulses and to the asymptotic phaseshifts of photoelectron wave packets. Special emphasis is laid on time-delay experiments, where attosecond XUV pulses are used to photoionize target atoms at well-defined times, followed by a probing process in real time by a phase-locked, infrared laser field. In this way, the laser field serves as a ‘clock’ to monitor the ionization event, but the observable delays do not correspond directly to the delay associated with single-photon ionization. Instead, a significant part of the observed delay originates from a measurement induced process, which obscures the single-photon ionization dynamics. This artefact is traced back to a phaseshift of the above-threshold ionization transition matrix element, which we call the continuum-continuum phase. It arises due to the laser-stimulated transitions between Coulomb continuum states. As we shall show here, these measurement-induced effects can be separated from the single-photon ionization process, using analytical expressions of universal character, so that eventually the attosecond time delays in photoionization can be accessed.

  7. Pulse shaper for electron gun control

    International Nuclear Information System (INIS)

    Modulation of electron gun of spectrometer for surface diagnostics allows to proceed to recording of N(E) from recording of the first derivative of secondary-emitted electron energy redistribution, dN/dE(E) with minimal modernization of the available modernization of the available receiving channel of spectrometer. Circuit with inductive bond ensures galvanic decoupling of the former by inlet and outlet. Irial spectra of characteristical losses in N(E) form obtained at modulation of the electron primary beam using the developed pulse former, and in dN/dE(E) form-using modulation of braking potential, are presented. 9 refs.; 2 figs

  8. Isolated attosecond soft X-rays and water window XAFS

    Science.gov (United States)

    Biegert, Jens

    2016-05-01

    We demonstrate generation of isolated attosecond soft X-ray pulses with duration less than 350 as at the carbon K-edge at 284 eV. This reproducible and CEP stable attosecond soft X-ray continuum covers the entire water window from 200 eV to 550 eV with a flux of 7.3x 107 photons/s and corresponds to a pulse energy of 2.9 pJ. We demonstrate the utility of our table-top source through soft X-ray near-edge fine-structure spectroscopy at K-shell absorption edges in condensed matter and retrieve the specific absorption features corresponding to the binding orbitals. We believe that these results herald attosecond material science by bridging the gap between ultrafast temporal resolution and element specific probing at the fundamental absorption edges of matter.

  9. Theoretical study of electronic damage in single particle imaging experiments at XFELs for pulse durations 0.1 - 10 fs

    CERN Document Server

    Gorobtsov, O Yu; Kabachnik, N M; Vartanyants, I A

    2015-01-01

    X-ray free-electron lasers (XFELs) may allow to employ the single particle imaging (SPI) method to determine the structure of macromolecules that do not form stable crystals. Ultrashort pulses of 10 fs and less allow to outrun complete disintegration by Coulomb explosion and minimize radiation damage due to nuclear motion, but electronic damage is still present. The major contribution to the electronic damage comes from the plasma generated in the sample that is strongly dependent on the amount of Auger ionization. Since the Auger process has a characteristic time scale on the order of femtoseconds, one may expect that its contribution will be significantly reduced for attosecond pulses. Here, we study the effect of electronic damage on the SPI at pulse durations from 0.1 fs to 10 fs and in a large range of XFEL fluences to determine optimal conditions for imaging of biological samples. We analyzed the contribution of different electronic excitation processes and found that at fluences higher than $10^{13}$-$...

  10. Compression of Electron Pulses for Femtosecond Electron Diffraction

    Science.gov (United States)

    Zandi, Omid; Yang, Jie; Centurion, Martin

    2014-05-01

    Our goal is to improve the temporal resolution in electron diffraction experiments to 100 fs by compressing the electron pulses using a time-varying electric field. The compressed pulse can be used for a better understanding of the dynamics of molecules under study. A bunch of 3 million electrons is generated at a photocathode by femtosecond UV laser pulses and accelerated to 100 keV in a static electric field. Then, the longitudinal component of the electric field of a microwave cavity is employed to compress the bunch. The cavity's frequency and phase are accurately tuned in such a way that the electric field is parallel to the bunch motion at its arrival and antiparallel to it at its exit. Compression in the transverse directions is done by magnetic lenses. Simulations have been done to predict the bunch profile at different positions and times by General Particle Tracer code. A streak camera has been built to measure the duration of the pulses. It uses the electric field of a discharging parallel plate capacitor to rotate the bunch so that angular spreading of the bunch is proportional to its duration. The capacitor is discharged by a laser pulse incident on a photo switch.

  11. Pulsed nuclear-electronic magnetic resonance

    CERN Document Server

    Morley, Gavin W; Mohammady, M Hamed; Aeppli, Gabriel; Kay, Christopher W M; Jeschke, Gunnar; Monteiro, Tania S

    2011-01-01

    Pulsed magnetic resonance is a wide-reaching technology allowing the quantum state of electronic and nuclear spins to be controlled on the timescale of nanoseconds and microseconds respectively. The time required to flip either dilute electronic or nuclear spins is orders of magnitude shorter than their decoherence times, leading to several schemes for quantum information processing with spin qubits. We investigate instead the novel regime where the eigenstates approximate 50:50 superpositions of the electronic and nuclear spin states forming "nuclear-electronic" qubits. Here we demonstrate quantum control of these states, using bismuth-doped silicon, in just 32 ns: orders of magnitude shorter than previous experiments where pure nuclear states were used. The coherence times of our states are over four orders of magnitude longer, being 1 ms or more at 8 K, and are limited by the naturally-occurring 29Si nuclear spin impurities. There is quantitative agreement between our experiments and no-free-parameter anal...

  12. Theoretical study of electronic damage in single-particle imaging experiments at x-ray free-electron lasers for pulse durations from 0.1 to 10 fs

    Science.gov (United States)

    Gorobtsov, O. Yu.; Lorenz, U.; Kabachnik, N. M.; Vartanyants, I. A.

    2015-06-01

    X-ray free-electron lasers (XFELs) may allow us to employ the single-particle imaging (SPI) method to determine the structure of macromolecules that do not form stable crystals. Ultrashort pulses of 10 fs and less allow us to outrun complete disintegration by Coulomb explosion and minimize radiation damage due to nuclear motion, but electronic damage is still present. The major contribution to the electronic damage comes from the plasma generated in the sample that is strongly dependent on the amount of Auger ionization. Since the Auger process has a characteristic time scale on the order of femtoseconds, one may expect that its contribution will be significantly reduced for attosecond pulses. Here we study the effect of electronic damage on the SPI at pulse durations from 0.1 to 10 fs and in a large range of XFEL fluences to determine optimal conditions for imaging of biological samples. We analyzed the contribution of different electronic excitation processes and found that at fluences higher than 1013- 10 15 photons /μ m2 (depending on the photon energy and pulse duration) the diffracted signal saturates and does not increase further. A significant gain in the signal is obtained by reducing the pulse duration from 10 to 1 fs. Pulses below a duration of 1 fs do not give a significant gain in the scattering signal in comparison with 1-fs pulses. We also study the limits imposed on SPI by Compton scattering.

  13. Attosecond experiments on plasmonic nanostructures principles and experiments

    CERN Document Server

    Schötz, Johannes

    2016-01-01

    Johannes Schötz presents the first measurements of optical electro-magnetic near-fields around nanostructures with subcycle-resolution. The ability to measure and understand light-matter interactions on the nanoscale is an important component for the development of light-wave-electronics, the control and steering of electron dynamics with the frequency of light, which promises a speed-up by several orders of magnitude compared to conventional electronics. The experiments presented here on metallic nanotips, widely used in experiments and applications, do not only demonstrate the feasibility of attosecond streaking as a unique tool for fundamental studies of ultrafast nanophotonics but also represent a first important step towards this goal. Contents Electron Scattering in Solids Attosecond Streaking from Metal Nanotips Target Groups Lecturers and students of physics, especially in the area of nanophotonics and attosecond physics About the Author Johannes Schötz received his Master's degree in physics and cu...

  14. Attosecond streaking in a nano-plasmonic field

    Science.gov (United States)

    Kelkensberg, F.; Koenderink, A. F.; Vrakking, M. J. J.

    2012-09-01

    A theoretical study of the application of attosecond streaking spectroscopy to time-resolved studies of the plasmonic fields surrounding isolated, resonantly excited spherical nanoparticles is presented. A classification of the different regimes in attosecond streaking is proposed and identified in our results that are derived from Mie calculations of plasmon fields, coupled to classical electron trajectory simulations. It is shown that in an attosecond streaking experiment, the electrons are almost exclusively sensitive to the component of the field parallel to the direction in which they are detected. This allows one to probe the different components of the field individually by resolving the angle of emission of the electrons. Finally, simulations based on fields calculated by finite-difference time-domain (FDTD) are compared with the results obtained using Mie fields. The two are found to be in good agreement with each other, supporting the notion that FDTD methods can be used to reliably investigate non-spherical structures.

  15. Attosecond streaking of photoelectron emission from disordered solids

    CERN Document Server

    Okell, W A; Fabris, D; Arrell, C A; Hengster, J; Ibrahimkutty, S; Seiler, A; Barthelmess, M; Stankov, S; Lei, D Y; Sonnefraud, Y; Rahmani, M; Uphues, Th; Maier, S A; Marangos, J P; Tisch, J W G

    2014-01-01

    Attosecond streaking of photoelectrons emitted by extreme ultraviolet light has begun to reveal how electrons behave during their transport within simple crystalline solids. Many sample types within nanoplasmonics, thin-film physics, and semiconductor physics, however, do not have a simple single crystal structure. The electron dynamics which underpin the optical response of plasmonic nanostructures and wide-bandgap semiconductors happen on an attosecond timescale. Measuring these dynamics using attosecond streaking will enable such systems to be specially tailored for applications in areas such as ultrafast opto-electronics. We show that streaking can be extended to this very general type of sample by presenting streaking measurements on an amorphous film of the wide-bandgap semiconductor tungsten trioxide, and on polycrystalline gold, a material that forms the basis of many nanoplasmonic devices. Our measurements reveal the near-field temporal structure at the sample surface, and photoelectron wavepacket te...

  16. 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.

  17. Theory of attosecond delays in laser-assisted photoionization

    Energy Technology Data Exchange (ETDEWEB)

    Dahlström, J.M., E-mail: marcus.dahlstrom@fysik.su.se [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); Atomic Physics, Fysikum, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm (Sweden); Guénot, D.; Klünder, K.; Gisselbrecht, M.; Mauritsson, J. [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); L’Huillier, A., E-mail: anne.lhuillier@fysik.lth.se [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); Maquet, A. [UPMC Université Paris 6, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, UMR 7614, LCPMR, Paris (France); Taïeb, R., E-mail: richard.taieb@upmc.fr [UPMC Université Paris 6, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, UMR 7614, LCPMR, Paris (France)

    2013-03-12

    Highlights: ► We find the phase for laser-assisted XUV ionization transition matrix elements (M). ► The phase of M is simply: the sum of the scattering phase of the intermediate continuum state and an universal phase. ► The universal phase is independent of the initial state and it leads to a delay observed in attosecond time-delay experiments. - Abstract: We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum–continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. The observed time-delay is a sum of two components: a one-photon Wigner-like delay and a universal delay that originates from the probing process itself.

  18. Theory of attosecond delays in laser-assisted photoionization

    International Nuclear Information System (INIS)

    Highlights: ► We find the phase for laser-assisted XUV ionization transition matrix elements (M). ► The phase of M is simply: the sum of the scattering phase of the intermediate continuum state and an universal phase. ► The universal phase is independent of the initial state and it leads to a delay observed in attosecond time-delay experiments. - Abstract: We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum–continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. The observed time-delay is a sum of two components: a one-photon Wigner-like delay and a universal delay that originates from the probing process itself

  19. Simulated Photoelectron-Based Imaging of Localized Surface Plasmons with Attosecond Resolution

    Science.gov (United States)

    Prell, James; Borja, Lauren; Gandman, Andrey; Whitmore, Desire; Neumark, Daniel; Leone, Stephen

    2013-03-01

    Simulations of proposed photoelectron streaking experiments in the presence of an oscillating plasmon field are presented. The results indicate that localized surface plasmon dephasing can be imaged with attosecond resolution using electron time-of-flight (TOF) or velocity map imaging (VMI) techniques. In the simulation, localized surface plasmons are excited in metal nanoparticles by a few-cycle infrared or visible laser pulse. Using time-delayed single, isolated attosecond x-ray pulses, electrons are photoemitted from the metallic nanoparticles and streaked by both the plasmon and laser electric fields. The effects of these two fields in the streaking spectra and images can be separated so that the temporal evolution of the plasmon electric field can be directly extracted. The plasmon electric field induces a broadening of the photoelectron speed distribution with an envelope directly proportional to that of the plasmon dipole moment. Plasmon-induced oscillation of the angular distribution in VMI is predicted to report the spatial distribution of the plasmon electric field for nanoparticles with high aspect ratios. The simulations indicate that these techniques can be used to map plasmon dynamics with unprecedented temporal resolution.

  20. Study on nanosecond pulsed electron beam generation

    Science.gov (United States)

    Ponomarev, D.; Kholodnaya, G.; Remnev, G.; Kaikanov, M.; Sazonov, R.

    2014-11-01

    The paper presents the findings of an investigation on volt-ampere characteristics of the diode with explosive emission cathodes of different constructions (blade metal-dielectric (MD-cathode) and solid graphite cathodes) under the change of the anode-cathode gap in wide ranges. The investigations were carried out using the TEA-500 pulsed electron accelerator. The total current of the electron beam was measured using the Faraday cup (FC). A 0.5-mm foiled glass fiber laminate was used as an emitting edge of the cathode in the experimental study with the explosive emission blade MD-cathode. Based on the obtained results, the conclusion was made that the graphite cathode has the most effective efficiency factor.

  1. Study on nanosecond pulsed electron beam generation

    International Nuclear Information System (INIS)

    The paper presents the findings of an investigation on volt-ampere characteristics of the diode with explosive emission cathodes of different constructions (blade metal-dielectric (MD-cathode) and solid graphite cathodes) under the change of the anode-cathode gap in wide ranges. The investigations were carried out using the TEA-500 pulsed electron accelerator. The total current of the electron beam was measured using the Faraday cup (FC). A 0.5-mm foiled glass fiber laminate was used as an emitting edge of the cathode in the experimental study with the explosive emission blade MD-cathode. Based on the obtained results, the conclusion was made that the graphite cathode has the most effective efficiency factor

  2. Multifrequency pulsed electron paramagnetic resonance on metalloproteins.

    Science.gov (United States)

    Lyubenova, Sevdalina; Maly, Thorsten; Zwicker, Klaus; Brandt, Ulrich; Ludwig, Bernd; Prisner, Thomas

    2010-02-16

    Metalloproteins often contain metal centers that are paramagnetic in some functional state of the protein; hence electron paramagnetic resonance (EPR) spectroscopy can be a powerful tool for studying protein structure and function. Dipolar spectroscopy allows the determination of the dipole-dipole interactions between metal centers in protein complexes, revealing the structural arrangement of different paramagnetic centers at distances of up to 8 nm. Hyperfine spectroscopy can be used to measure the interaction between an unpaired electron spin and nuclear spins within a distance of 0.8 nm; it therefore permits the characterization of the local structure of the paramagnetic center's ligand sphere with very high precision. In this Account, we review our laboratory's recent applications of both dipolar and hyperfine pulsed EPR methods to metalloproteins. We used pulsed dipolar relaxation methods to investigate the complex of cytochrome c and cytochrome c oxidase, a noncovalent protein-protein complex involved in mitochondrial electron-transfer reactions. Hyperfine sublevel correlation spectroscopy (HYSCORE) was used to study the ligand sphere of iron-sulfur clusters in complex I of the mitochondrial respiratory chain and substrate binding to the molybdenum enzyme polysulfide reductase. These examples demonstrate the potential of the two techniques; however, they also highlight the difficulties of data interpretation when several paramagnetic species with overlapping spectra are present in the protein. In such cases, further approaches and data are very useful to enhance the information content. Relaxation filtered hyperfine spectroscopy (REFINE) can be used to separate the individual components of overlapping paramagnetic species on the basis of differences in their longitudinal relaxation rates; it is applicable to any kind of pulsed hyperfine or dipolar spectroscopy. Here, we show that the spectra of the iron-sulfur clusters in complex I can be separated by this

  3. Development of extreme ultraviolet and soft x-ray multilayer optics for scientific studies with femtosecond/attosecond sources

    Energy Technology Data Exchange (ETDEWEB)

    Aquila, Andrew Lee [Univ. of California, Berkeley, CA (United States)

    2009-05-21

    The development of multilayer optics for extreme ultraviolet (EUV) radiation has led to advancements in many areas of science and technology, including materials studies, EUV lithography, water window microscopy, plasma imaging, and orbiting solar physics imaging. Recent developments in femtosecond and attosecond EUV pulse generation from sources such as high harmonic generation lasers, combined with the elemental and chemical specificity provided by EUV radiation, are opening new opportunities to study fundamental dynamic processes in materials. Critical to these efforts is the design and fabrication of multilayer optics to transport, focus, shape and image these ultra-fast pulses This thesis describes the design, fabrication, characterization, and application of multilayer optics for EUV femtosecond and attosecond scientific studies. Multilayer mirrors for bandwidth control, pulse shaping and compression, tri-material multilayers, and multilayers for polarization control are described. Characterization of multilayer optics, including measurement of material optical constants, reflectivity of multilayer mirrors, and metrology of reflected phases of the multilayer, which is critical to maintaining pulse size and shape, were performed. Two applications of these multilayer mirrors are detailed in the thesis. In the first application, broad bandwidth multilayers were used to characterize and measure sub-100 attosecond pulses from a high harmonic generation source and was performed in collaboration with the Max-Planck institute for Quantum Optics and Ludwig- Maximilians University in Garching, Germany, with Professors Krausz and Kleineberg. In the second application, multilayer mirrors with polarization control are useful to study femtosecond spin dynamics in an ongoing collaboration with the T-REX group of Professor Parmigiani at Elettra in Trieste, Italy. As new ultrafast x-ray sources become available, for example free electron lasers, the multilayer designs

  4. 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

  5. Small compact pulsed electron source for radiation technologies

    International Nuclear Information System (INIS)

    The small compact pulsed electron source for radiation technologies is considered in the report. The electron source consists of pulsed high voltage Marx generator and vacuum diode with explosive emission cathode. The main parameters of electron source are next: kinetic energy is 100-150 keV, beam current is 5-200 A and pulse duration is 100-400 nsec. The distribution of absorbed doses in irradiated materials is considered. The physical feasibility of pulsed low energy electron beam for applications is considered

  6. Can strong-field ionization prepare attosecond dynamics?

    CERN Document Server

    Pabst, Stefan

    2015-01-01

    Strong-field ionization (SFI) has been shown to prepare wave packets with few-femtosecond periods. Here, we explore whether this technique can be extended to the attosecond time scale. We introduce an intuitive model for predicting the bandwidth of ionic states that can be coherently prepared by SFI. This bandwidth is given by the Fourier-transformed sub-cycle SFI rate and decreases considerably with increasing central wavelength of the ionizing pulse. Many-body calculations based on time-dependent configuration-interaction singles (TDCIS) quantitatively support this result and reveal an additional decrease of the bandwidth as a consequence of channel interactions and non-adiabatic dynamics. Our results further predict that multi-cycle femtosecond pulses can coherently prepare attosecond wave packets with higher selectivity and versatility compared to single-cycle pulses.

  7. Enhanced subthreshold electron-positron production in short laser pulses

    OpenAIRE

    Titov, A. I.; Takabe, H.; Kampfer, B.; Hosaka, A.

    2012-01-01

    The emission of electron-positron pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g.\\ laser) wave field is analyzed. A significant increase of the total cross section of pair production in the subthreshold region is found for decreasing laser pulse duration even in case of moderate laser pulse intensities.

  8. The Electron Trajectory in a Relativistic Femtosecond Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    He Feng; Yu Wei; Lu Peixiang; Xu Han; Shen Baifei; Li Ruxin; Xu Zhizhan

    2005-01-01

    In this report, we start from Lagrange equation and analyze theoretically the electron dynamics in electromagnetic field. By solving the relativistic government equations of electron,the trajectories of an electron in plane laser pulse, focused laser pulse have been given for different initial conditions. The electron trajectory is determined by its initial momentum, the amplitude,spot size and polarization of the laser pulse. The optimum initial momentum of the electron for LSS (laser synchrotron source) is obtained. Linear polarized laser is more advantaged than circular polarized laser for generating harmonic radiation.

  9. Development of a high current short pulse electron gun

    International Nuclear Information System (INIS)

    Dielectric wall accelerator (DWA), towards high gradient acceleration field (30 MeV/m-100 MeV/m), is under development at Institute of Modern Physics. A prototype was designed and constructed to prove the principle. This needs a short pulse high current electron source to match the acceleration field generated by the Blumlein-type pulse forming lines (PFLs). In this paper, we report the design and test of a new type short pulse high current electron gun based on principle of vacuum arc discharge. Electron beams of 100 mA with pulse width of 10 ns were obtained. (authors)

  10. Electronic Patch Wireless Reflectance Pulse Oximetry for Remote Health Monitoring .

    OpenAIRE

    Venkatesh, S.

    2013-01-01

    This project describes the development of a wireless electronic patch for wearable health monitoring by reflectance pulse oximetry. The Electronic Patch is the health monitoring system which incorporates the biomedical sensors, detectors, communication system, and a battery in a polymer based material that will hold all the components by safely. The Electronic Patch is accompanied with a new optical biomedical sensor for reflectance pulse oximetry so that the Electronic Patch in this case can...

  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. Generation of ultrashort electron bunches by colliding laser pulses

    International Nuclear Information System (INIS)

    A proposed laser-plasma based relativistic electron source [E. Esarey et al., Phys. Rev. Lett. 79, 2682 (1997)] using laser triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counter-propagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses

  13. Modulation of attosecond beating in resonant two-photon ionization

    CERN Document Server

    Galán, Álvaro J; Martín, Fernando

    2014-01-01

    We present a theoretical study of the photoelectron attosecond beating at the basis of RABBIT (Reconstruction of Attosecond Beating By Interference of Two-photon transitions) in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, its sidebands exhibit a peaked phase shift as well as a modulation of the beating frequency itself. Furthermore, the beating between two resonant paths persists even when the pump and the probe pulses do not overlap, thus providing a sensitive non-holographic interferometric means to reconstruct coherent metastable wave packets. We characterize these phenomena quantitatively with a general finite-pulse analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes, at a negligible computational cost. The model predictions are in excellent agreement with those of accurate ab initio calculations for the helium atom in the region of the N=2 doubly excited states.

  14. Quantum description and properties of electrons emitted from pulsed nanotip electron sources

    OpenAIRE

    Lougovski, Pavel; Batelaan, Herman

    2011-01-01

    We present a quantum calculation of the electron degeneracy for electron sources. We explore quantum interference of electrons in the temporal and spatial domain and demonstrate how it can be utilized to characterize a pulsed electron source. We estimate effects of Coulomb repulsion on two-electron interference and show that currently available nano tip pulsed electron sources operate in the regime where the quantum nature of electrons can be made dominant.

  15. Pulse Splitting in Short Wavelength Seeded Free Electron Lasers

    International Nuclear Information System (INIS)

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

  16. Preparing attosecond coherences by strong-field ionization

    OpenAIRE

    Pabst, Stefan; Lein, Manfred; Wörner, Hans Jakob

    2016-01-01

    Strong-field ionization (SFI) has been shown to prepare wave packets with few-femtosecond periods. Here, we explore whether this technique can be extended to the attosecond time scale. We introduce an intuitive model, which is based on the Fourier transform of the subcycle SFI rate, for predicting the bandwidth of ionic states that can be coherently prepared by SFI. The coherent bandwidth decreases considerably with increasing central wavelength of the ionizing pulse but it is much less sensi...

  17. A pulse radiolysis study on electron affinity of piperonal

    Institute of Scientific and Technical Information of China (English)

    MA; Jianhua; LIN; Weizhen; WANG; Wenfeng; YAO; Side

    2005-01-01

    The piperonal electron affinity was studied using pulse radiolysis technique. The electron transfer reaction process between piperonal and anthraquinone-2-sulfate was observed in the pH 7 phosphoric acid salt buffer. The transient absorption spectra of electron transfer reaction between piperonal and anthraquinone-2-sulfate were obtained, and the initial proof of the electron transfer between electron donor and acceptor was provided directly. The one-electron reduction potential of piperonal was determined to be -0.457 V.

  18. Direct evidences for inner-shell electron-excitation by laser induced electron recollision

    CERN Document Server

    Deng, Yunpei; Jia, Zhengmao; Komm, Pavel; Zheng, Yinhui; Ge, Xiaochun; Li, Ruxin; Marcus, Gilad

    2015-01-01

    Extreme ultraviolet (XUV) attosecond pulses, generated by a process known as laser-induced electron recollision, are a key ingredient for attosecond metrology, providing a tool to precisely initiate and probe sub-femtosecond dynamics in the microcosms of atoms, molecules and solids[1]. However, with the current technology, extending attosecond metrology to scrutinize the dynamics of the inner-shell electrons is a challenge, that is because of the lower efficiency in generating the required soft x-ray \\hbar\\omega>300 eV attosecond bursts and the lower absorption cross-sections in this spectral range. A way around this problem is to use the recolliding electron to directly initiate the desired inner-shell process, instead of using the currently low flux x-ray attosecond sources.Such an excitation process occurs in a sub-femtosecond timescale, and may provide the necessary "pump" step in a pump-probe experiment[2]. Here we used a few cycle infrared \\lambda_{0}~1800nm source[3] and observed direct evidences for i...

  19. Single-Shot Femtosecond Electron Diffraction with Laser-Accelerated Electrons: Experimental Demonstration of Electron Pulse Compression

    International Nuclear Information System (INIS)

    We report the first experimental demonstration of longitudinal compression of laser-accelerated electron pulses. Accelerated by a femtosecond laser pulse with an intensity of 1018 W/cm2, an electron pulse with an energy of around 350 keV and a relative momentum spread of about 10-2 was compressed to a 500-fs pulse at a distance of about 50 cm from the electron source by using a magnetic pulse compressor. This pulse was used to generate a clear diffraction pattern of a gold crystal in a single shot. This method solves the space-charge problem in ultrafast electron diffraction.

  20. Theory of attosecond delays in laser-assisted photoionization

    CERN Document Server

    Dahlström, J M; Klünder, K; Gisselbrecht, M; Mauritsson, J; L'Huillier, A; Maquet, A; Taïeb, R

    2011-01-01

    We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum--continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. This makes clear that the observed time-delays...

  1. Attosecond beamline with actively stabilized and spatially separated beam paths

    Science.gov (United States)

    Huppert, M.; Jordan, I.; Wörner, H. J.

    2015-12-01

    We describe a versatile and compact beamline for attosecond spectroscopy. The setup consists of a high-order harmonic source followed by a delay line that spatially separates and then recombines the extreme-ultraviolet (XUV) and residual infrared (IR) pulses. The beamline introduces a controlled and actively stabilized delay between the XUV and IR pulses on the attosecond time scale. A new active-stabilization scheme combining a helium-neon-laser and a white-light interferometer minimizes fluctuations and allows to control delays accurately (26 as rms during 1.5 h) over long time scales. The high-order-harmonic-generation region is imaged via optical systems, independently for XUV and IR, into an interaction volume to perform pump-probe experiments. As a consequence of the spatial separation, the pulses can be independently manipulated in intensity, polarization, and frequency content. The beamline can be combined with a variety of detectors for measuring attosecond dynamics in gases, liquids, and solids.

  2. Realizing Ultrafast Electron Pulse Self-Compression by Femtosecond Pulse Shaping Technique.

    Science.gov (United States)

    Qi, Yingpeng; Pei, Minjie; Qi, Dalong; Yang, Yan; Jia, Tianqing; Zhang, Shian; Sun, Zhenrong

    2015-10-01

    Uncorrelated position and velocity distribution of the electron bunch at the photocathode from the residual energy greatly limit the transverse coherent length and the recompression ability. Here we first propose a femtosecond pulse-shaping method to realize the electron pulse self-compression in ultrafast electron diffraction system based on a point-to-point space-charge model. The positively chirped femtosecond laser pulse can correspondingly create the positively chirped electron bunch at the photocathode (such as metal-insulator heterojunction), and such a shaped electron pulse can realize the self-compression in the subsequent propagation process. The greatest advantage for our proposed scheme is that no additional components are introduced into the ultrafast electron diffraction system, which therefore does not affect the electron bunch shape. More importantly, this scheme can break the limitation that the electron pulse via postphotocathode static compression schemes is not shorter than the excitation laser pulse due to the uncorrelated position and velocity distribution of the initial electron bunch. PMID:26722884

  3. Two mirror X-ray pulse split and delay instrument for femtosecond time resolved investigations at the LCLS free electron laser facility.

    Science.gov (United States)

    Berrah, Nora; Fang, Li; Murphy, Brendan F; Kukk, Edwin; Osipov, Timur Y; Coffee, Ryan; Ferguson, Ken R; Xiong, Hui; Castagna, Jean-Charles; Petrovic, Vlad S; Montero, Sebastian Carron; Bozek, John D

    2016-05-30

    We built a two-mirror based X-ray split and delay (XRSD) device for soft X-rays at the Linac Coherent Light Source free electron laser facility. The instrument is based on an edge-polished mirror design covering an energy range of 250 eV-1800 eV and producing a delay between the two split pulses variable up to 400 femtoseconds with a sub-100 attosecond resolution. We present experimental and simulation results regarding molecular dissociation dynamics in CH3I and CO probed by the XRSD device. We observed ion kinetic energy and branching ratio dependence on the delay times which were reliably produced by the XRSD instrument. PMID:27410102

  4. Two mirror X-ray pulse split and delay instrument for femtosecond time resolved investigations at the LCLS free electron laser facility.

    Science.gov (United States)

    Berrah, Nora; Fang, Li; Murphy, Brendan F; Kukk, Edwin; Osipov, Timur Y; Coffee, Ryan; Ferguson, Ken R; Xiong, Hui; Castagna, Jean-Charles; Petrovic, Vlad S; Montero, Sebastian Carron; Bozek, John D

    2016-05-30

    We built a two-mirror based X-ray split and delay (XRSD) device for soft X-rays at the Linac Coherent Light Source free electron laser facility. The instrument is based on an edge-polished mirror design covering an energy range of 250 eV-1800 eV and producing a delay between the two split pulses variable up to 400 femtoseconds with a sub-100 attosecond resolution. We present experimental and simulation results regarding molecular dissociation dynamics in CH3I and CO probed by the XRSD device. We observed ion kinetic energy and branching ratio dependence on the delay times which were reliably produced by the XRSD instrument.

  5. 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...

  6. 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.

  7. Transient of power pulse and its sequence in power electronics

    Institute of Scientific and Technical Information of China (English)

    ZHAO ZhengMing; BAI Hua; YUAN LiQiang

    2007-01-01

    Various failures and destructions occur in the applications of the power electronic converter, The real practice shows that these failures are connected with the concentration of the transient power pulse. In allusion to the physical characteristics of power electronic converters, this paper proposed that the power pulse and its sequence are the basis for power electronics in the perspective of electromagnetic energy. The authors analyzed the transient processes in the power semiconductors,electric conduction loops and controller system and illustrated the power pulse phenomena in high voltage and high power inverters. This investigation on the power pulse sequence is very meaningful for the failure analysis and device protection and has become an important topic in power electronics.

  8. Transient of power pulse and its sequence in power electronics

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Various failures and destructions occur in the applications of the power electronic converter. The real practice shows that these failures are connected with the con-centration of the transient power pulse. In allusion to the physical characteristics of power electronic converters,this paper proposed that the power pulse and its se-quence are the basis for power electronics in the perspective of electromagnetic energy. The authors analyzed the transient processes in the power semiconductors,electric conduction loops and controller system and illustrated the power pulse phenomena in high voltage and high power inverters. This investigation on the power pulse sequence is very meaningful for the failure analysis and device pro-tection and has become an important topic in power electronics.

  9. Attosecond Timing in Optical-to-Electrical Conversion

    CERN Document Server

    Baynes, Fred N; Fortier, Tara; Zhou, Qiugui; Beling, Andreas; Campbell, Joe C; Diddames, Scott A

    2014-01-01

    The most frequency-stable sources of electromagnetic radiation are produced optically, and optical frequency combs provide the means for high fidelity frequency transfer across hundreds of terahertz and into the microwave domain. A critical step in this photonic-based synthesis of microwave signals is the optical-to-electrical conversion process. Here we show that attosecond (as) timing stability can be preserved across the opto-electronic interface of a photodiode, despite an intrinsic temporal response that is more than six orders of magnitude slower. The excess timing noise in the photodetection of a periodic train of ultrashort optical pulses behaves as flicker noise (1/f) with amplitude of 4 as/Sqrt(Hz) at 1 Hz offset. The corresponding fractional frequency fluctuations are 1.4x10-17 at 1 second and 5.5x10-20 at 1000 seconds. These results demonstrate that direct photodetection, as part of frequency-comb-based microwave synthesis, can support the timing performance of the best optical frequency standards...

  10. 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...

  11. Apparatus and method for generating high density pulses of electrons

    International Nuclear Information System (INIS)

    An apparatus and method are described for the production of high density pulses of electrons using a laser energized emitter. Caesium atoms from a low pressure vapour atmosphere are absorbed on and migrate from a metallic target rapidly heated by a laser to a high temperature. Due to this heating time being short compared with the residence time of the caesium atoms adsorbed on the target surface, copious electrons are emitted which form a high current density pulse. (U.K.)

  12. Use of photoelectron laser phase determination method for attosecond measurements with quantum-mechanical calculations

    Institute of Scientific and Technical Information of China (English)

    Ge Yu-Cheng

    2008-01-01

    This paper calculates quantum-mechanically the photoelectron energy spectra excited by attosecond x-rays in the presence of a few-cycle laser. A photoelectron laser phase determination method is used for precise measurements of the pulse natural properties of x-ray intensity and the instantaneous frequency profiles. As a direct procedure without any previous pulse profile assumptions and time-resolved measurements as well as data fitting analysis, this method can be used to improve the time resolutions of attosecond timing and measurements with metrological precision. The measurement range is half of a laser optical cycle.

  13. Laser assisted electron dynamics

    CERN Document Server

    Bray, Alexander William

    2016-01-01

    We apply the convergent close-coupling (CCC) formalism to analyse the processes of laser assisted electron impact ionisation of He, and the attosecond time delay in the photodetachment of the H^{-} ion and the photoionisation of He. Such time dependent atomic collision processes are of considerable interest as experimental measurements on the relevant timescale (attoseconds 10^{-18} s) are now possible utilising ultrafast and intense laser pulses. These processes in particular are furthermore of interest as they are strongly influenced by many-electron correlations. In such cases their theoretical description requires a more comprehensive treatment than that offered by first order perturbation theory. We apply such a treatment through the use of the CCC formalism which involves the complete numeric solution of the integral Lippmann-Schwinger equations pertaining to a particular scattering event. For laser assisted electron impact ionisation of He such a treatment is of a considerably greater accuracy than the...

  14. Two-pulse laser control of nuclear and electronic motion

    DEFF Research Database (Denmark)

    Grønager, Michael; Henriksen, Niels Engholm

    1997-01-01

    We discuss an explicitly time-dependent two-pulse laser scheme for controlling where nuclei and electrons are going in unimolecular reactions. We focus on electronic motion and show, with HD+ as an example, that one can find non-stationary states where the electron (with some probability......) oscillates back and forth between the two nuclei. We discuss how this finding can be used in a scheme for controlling electron transfer in real-time. (C) 1997 Elsevier Science B.V....

  15. 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

  16. Intensity dependence of laser-assisted atto-second photoionization spectra

    International Nuclear Information System (INIS)

    We study experimentally the influence of the intensity of the infrared (IR) probe field on atto-second pulse train (APT) phase measurements performed with the RABITT method (Reconstruction of atto-second Beating by Interference in Two-Photon Transitions). We find that if a strong IR field is applied, the atto-second pulses will appear to have lower-than-actual chirp rates. We also observe the onset of the streaking regime in the breakdown of the weak-field RABITT conditions. We perform a Fourier-analysis of harmonic and sideband continuum states and show that the mutual phase relation of the harmonics can be extracted from higher Fourier components. (authors)

  17. Progress in sub-femtosecond control of electron localization in molecules

    Indian Academy of Sciences (India)

    Kamal P Singh

    2014-01-01

    Recent advances in controlled generation of intense, ultrashort laser pulses in the femtosecond and attosecond time-scales have pushed new avenues of research in the coherent control of ultrafast electron dynamics in atoms and molecules. We present a topical review on the phenomenon of control of electron localization in small dissociating molecules. By creating and controlling coherent superposition of the symmetric and antisymmetric electronic states, it becomes possible to confine the evolving electron cloud onto a preferred nucleus, thereby steering the molecule towards a desired dissociation route. We discuss the origin of the idea and various mechanisms to achieve electron localization in small molecules. To highlight recent experimental progress, we explain how one can employ few-cycle IR pulses and different attosecond extreme ultraviolet (EUV) pulses in various ways to successfully demonstrate the control of electronic dynamics. Future research opportunities and challenges on this topic are envisioned.

  18. AXSIS: Exploring the frontiers in attosecond X-ray science, imaging and spectroscopy

    Science.gov (United States)

    Kärtner, F. X.; Ahr, F.; Calendron, A.-L.; Çankaya, H.; Carbajo, S.; Chang, G.; Cirmi, G.; Dörner, K.; Dorda, U.; Fallahi, A.; Hartin, A.; Hemmer, M.; Hobbs, R.; Hua, Y.; Huang, W. R.; Letrun, R.; Matlis, N.; Mazalova, V.; Mücke, O. D.; Nanni, E.; Putnam, W.; Ravi, K.; Reichert, F.; Sarrou, I.; Wu, X.; Yahaghi, A.; Ye, H.; Zapata, L.; Zhang, D.; Zhou, C.; Miller, R. J. D.; Berggren, K. K.; Graafsma, H.; Meents, A.; Assmann, R. W.; Chapman, H. N.; Fromme, P.

    2016-09-01

    -, accelerator,- X-ray scientists as well as spectroscopists and biochemists optimizes X-ray pulse parameters, in tandem with sample delivery, crystal size, and advanced X-ray detectors. Ultimately, the new capability, attosecond serial X-ray crystallography and spectroscopy, will be applied to one of the most important problems in structural biology, which is to elucidate the dynamics of light reactions, electron transfer and protein structure in photosynthesis.

  19. Generation of ultrashort electron bunches by colliding laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, C.B.; Lee, P.B.; Wurtele, J.S. [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States); Esarey, E. [Beam Physics Branch, Plasma Physics Division, Navel Research Laboratory, Washington, District of Columbia 20375 (United States); Leemans, W.P. [Center for Beam Physics, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    1999-07-01

    A proposed laser-plasma based relativistic electron source [E. Esarey {ital et al.}, Phys. Rev. Lett. {bold 79}, 2682 (1997)] using laser triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counter-propagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses. {copyright} {ital 1999 American Institute of Physics.}

  20. Design and development of pulsed electron beam accelerator 'AMBICA - 600'

    Science.gov (United States)

    Verma, Rishi; Deb, Pankaj; Shukla, Rohit; Sharma, Surender; Shyam, Anurag

    2012-11-01

    Short duration, high power pulses with fast rise time and good flat-top are essentially required for driving pulsed electron beam diodes. To attain this objective, a dual resonant Tesla transformer based pulsed power accelerator 'AMBICA-600' has been developed. In this newly developed system, a coaxial water line is charged through single turn Tesla transformer that operates in the dual resonant mode. For making the accelerator compact, in the high power pulse forming line, water has been used as dielectric medium because of its high dielectric constant, high dielectric strength and high energy density. The coaxial waterline can be pulsed charged up to 600kV, has impedance of ~5Ω and generates pulse width of ~60ns. The integrated system is capable of producing intense electron beam of 300keV, 60kA when connected to impedance matched vacuum diode. In this paper, system hardware details and experimental results of gigawatt electron beam generation have been presented.

  1. Ultrafast Relaxation Dynamics of Highly-excited States in N2 Molecules Excited by Femtosecond XUV Pulses

    Directory of Open Access Journals (Sweden)

    Vrakking Marc J.J.

    2013-03-01

    Full Text Available We used velocity-map-imaging to measure electronic and nuclear dynamics in N2 molecules excited by a train of attosecond pulses. A time-to-space mapping of autoionization channel is demonstrated. It is found that the autoionization becomes energetically allowed when the two nuclei are still very close (~ 3 Å and that it can be coherently manipulated by a strong femtosecond infrared pulse.

  2. Velvet's multi-pulsed emission and multi-pulsed electron beams

    Institute of Scientific and Technical Information of China (English)

    Xia Lian-Sheng; Zhang Huang; Chen De-Biao; Zhaug Kai-Zhi; Shi Jin-Shui; Zhang Lin-Wen

    2005-01-01

    The velvet electron emission characteristics and beams' brightness are investigated with a multi-pulsed mode. The results indicate that in the multi-pulsed mode the velvet emission is not uniform and the periphery emission is much stronger than that from the centre. The periphery emission contributes much more to the formation of the cathode plasma than the centre emission, which leads to diode impendence breakdown. The relationship between the cathode plasma expansion and the initial emittance of the cathode is deduced to describe the characteristics of the multi-pulsed vacuum diode. The emittance of the multi-pulsed beams is measured to be less than 1000mm.mrad. The brightness of the electron beams is better than 1×108A/(M·rad)2.

  3. Synchronization of Sub-Picosecond Electron and Laser Pulses

    International Nuclear Information System (INIS)

    Sub-picosecond laser-electron synchronization is required to take full advantage of the experimental possibilities arising from the marriage of modern high intensity lasers and high brightness electron beams in the same laboratory. Two particular scenarios stand out in this regard, injection of ultra-short electron pulses in short wavelength laser-driven plasma accelerators, and Compton scattering of laser photons from short electron pulses. Both of these applications demand synchronization, which is subpicosecond, with tens of femtosecond synchronization implied for next-generation experiments. Typically, an RF electron accelerator is synchronized to a short pulse laser system by detecting the repetition signal of a laser oscillator, adjusted to an exact subharmonic of the linac RF frequency, and multiplying or phase locking this signal to produce the master RF clock. Pulse-to-pulse jitter characteristic of self-mode-locked laser oscillators represents a direct contribution to the ultimate timing jitter between a high intensity laser focus and electron beam at the interaction point, or a photocathode drive laser in an RF photoinjector. This timing jitter problem has been addressed most seriously in the context of the RF photoinjector, where the electron beam properties are sensitive functions of relative timing jitter. The timing jitter achieved in synchronized photocathode drive laser systems is near, or slightly below one picosecond. The ultimate time of arrival jitter of the beam at the photoinjector exit is typically a bit smaller than the photocathode drive-laser jitter due to velocity compression effects in the first RF cell of the gun. This tendency of the timing of the electron beam arrival at a given spatial point to lock to the RF lock is strongly reinforced by use of magnetic compression

  4. Excitation of muonic molecules ddμ and dtμ by super-intense attosecond soft X-ray laser pulses: shaped post-laser-pulse muonic oscillations and enhancement of nuclear fusion

    International Nuclear Information System (INIS)

    The quantum dynamics of muonic molecular ions ddμ and dtμ excited by linearly polarized along the molecular (z)-axis super-intense laser pulses is studied beyond the Born–Oppenheimer approximation by the numerical solution of the time-dependent Schroedinger equation within a three-dimensional model, including the internuclear distance R and muon coordinates z and ρ. The peak-intensity of the super-intense laser pulses used in our simulations is I0 = 3.51 × 1022 W/cm2 and the wavelength is λl = 5 nm. In both ddμ and dtμ, expectation values〈z〉 and 〈ρ〉 of muon demonstrate “post-laser-pulse” oscillations after the ends of the laser pulses. In ddμ post-laser-pulse z-oscillations appear as shaped nonoverlapping “echo-pulses”. In dtμ post-laser-pulse muonic z-oscillations appear as comparatively slow large-amplitude oscillations modulated with small-amplitude pulsations. The post-laser-pulse ρ-oscillations in both ddμ and dtμ appear, for the most part, as overlapping “echo-pulses”. The post-laser-pulse oscillations do not occur if the Born–Oppenheimer approximation is employed. Power spectra generated due to muonic motion along both optically active z and optically passive ρ degrees of freedom are calculated. The fusion probability in dtμ can be increased by more than 11 times by making use of three sequential super-intense laser pulses. The energy released from the dt fusion in dtμ can by more than 20 GeV exceed the energy required to produce a usable muon and the energy of the laser pulses used to enhance the fusion. The possibility of power production from the laser-enhanced muon-catalyzed fusion is discussed. (author)

  5. Two-electron quantum ring in short pulses

    Institute of Scientific and Technical Information of China (English)

    Poonam Silotia; Rakesh Kumar Meena; Vinod Prasad

    2015-01-01

    The response of two-electron quantum ring system to the short laser pulses of different shapes in the presence of external static electric field is studied. The variation of transition probabilities of the two-electron quatum ring from ground state to excited states with a number of parameters is shown and explained. The energy levels and wavefunctions of the system in the presence of static electric field are found by solving the time-independent Schr ¨odinger equation numerically by finite difference method. The shape of the pulse plays a dominant role on the dynamics.

  6. Nanosecond length electron pulses from a laser-excited photocathode

    International Nuclear Information System (INIS)

    A photocathode made from polycrystalline lanthanum hexaboride (LaB6) has produced nanosecond length electron pulses when excited by an excimer laser at 308nm. Peak currents in excess of 1A have been observed, with quantum yields of 4 x 10-5 being measured. A method for extracting the electrons from an emission-limited cathode, plasma extraction, has been demonstrated. This technique uses a low power continuous discharge to provide the electric field needed to extract the photoelectrons. This technique may be useful in producing high repetition rate short pulse ion sources. 10 refs., 4 figs

  7. Controlled electron emission and vacuum breakdown with nanosecond pulses

    Science.gov (United States)

    Seznec, B.; Dessante, Ph; Caillault, L.; Babigeon, J.-L.; Teste, Ph; Minea, T.

    2016-06-01

    Vacuum electron sources exploiting field emission are generally operated in direct current (DC) mode. The development of nanosecond and sub-nanosecond pulsed power supplies facilitates the emission of compact bunches of electrons of high density. The breakdown level is taken as the highest value of the voltage avoiding the thermo-emission instability. The effect of such ultra-fast pulses on the breakdown voltage and the emitted electron current is discussed as a result of the thermo-emission modelling applied to a significant protrusion. It is found that pulsing very rapidly the vacuum breakdown occurs at higher voltage values than for the DC case, because it rises faster than the heat diffusion. In addition, the electron emission current increases significantly regardless of the theoretical approach is used. A comparative study of this theoretical work is discussed for several different forms of the protrusion (elliptic and hyperbolic) and different metals (hence varying the melting point), particularly refractory (tungsten) versus conductor (titanium). Pulsed mode operation can provide an increase on breakdown voltage (up to 18%) and a significant increase (up to 330%) of the electron extracted current due to its high non-linear dependency with the voltage, for the case for the case with a hyperbolic protrusion.

  8. Detection of pulsed neutrons with solid-state electronics

    Science.gov (United States)

    Chatzakis, J.; Rigakis, I.; Hassan, S. M.; Clark, E. L.; Lee, P.

    2016-09-01

    Measurements of the spatial and time-resolved characteristics of pulsed neutron sources require large area detection materials and fast circuitry that can process the electronic pulses readout from the active region of the detector. In this paper, we present a solid-state detector based on the nuclear activation of materials by neutrons, and the detection of the secondary particle emission of the generated radionuclides’ decay. The detector utilizes a microcontroller that communicates using a modified SPI protocol. A solid-state, pulse shaping filter follows a charge amplifier, and it is designed as an inexpensive, low-noise solution for measuring pulses measured by a digital counter. An imaging detector can also be made by using an array of these detectors. The system can communicate with an interface unit and pass an image to a personal computer.

  9. Development of an (e,2e) electron momentum spectroscopy apparatus using an ultrashort pulsed electron gun

    International Nuclear Information System (INIS)

    An (e,2e) apparatus for electron momentum spectroscopy (EMS) has been developed, which employs an ultrashort-pulsed incident electron beam with a repetition rate of 5 kHz and a pulse duration in the order of a picosecond. Its instrumental design and technical details are reported, involving demonstration of a new method for finding time-zero. Furthermore, EMS data for the neutral Ne atom in the ground state measured by using the pulsed electron beam are presented to illustrate the potential abilities of the apparatus for ultrafast molecular dynamics, such as by combining EMS with the pump-and-probe technique.

  10. Attosecond delays in photoionization: time and quantum mechanics

    Science.gov (United States)

    Maquet, Alfred; Caillat, Jérémie; Taïeb, Richard

    2014-10-01

    This article addresses topics regarding time measurements performed on quantum systems. The motivation is linked to the advent of ‘attophysics’ which makes feasible to follow the motion of electrons in atoms and molecules, with time resolution at the attosecond (1 as = 10-18 s) level, i.e. at the natural scale for electronic processes in these systems. In this context, attosecond ‘time-delays’ have been recently measured in experiments on photoionization and the question arises if such advances could cast a new light on the still active discussion on the status of the time variable in quantum mechanics. One issue still debatable is how to decide whether one can define a quantum time operator with eigenvalues associated to measurable ‘time-delays’, or time is a parameter, as it is implicit in the Newtonian classical mechanics. One objective of this paper is to investigate if the recent attophysics-based measurements could shed light on this parameter-operator conundrum. To this end, we present here the main features of the theory background, followed by an analysis of the experimental schemes that have been used to evidence attosecond ‘time-delays’ in photoionization. Our conclusion is that these results reinforce the view that time is a parameter which cannot be defined without reference to classical mechanics.

  11. The envelope Hamiltonian for electron interaction with ultrashort pulses

    CERN Document Server

    Toyota, Koudai; Rost, Jan M

    2014-01-01

    For ultrashort VUV pulses with a pulse length comparable to the orbital time of the bound electrons they couple to we propose a simplified envelope Hamiltonian. It is based on the Kramers-Henneberger representation in connection with a Floquet expansion of the strong-field dynamics but keeps the time dependence of the pulse envelope explicit. Thereby, the envelope Hamiltonian captures the essence of the physics, -- light-induced shifts of bound states, single-photon absorption, and non-adiabatic electronic transitions. It delivers quantitatively accurate ionization dynamics and allows for physical insight into the processes occurring. Its minimal requirements for construction in terms of laser parameters make it ideally suited for a large class of atomic and molecular problems.

  12. Study on surface treatment by pulsed electron beams

    International Nuclear Information System (INIS)

    We developed a pulsed electron beam system for surface treatment use. It features high peak power density and broad area beams, which result in the possibility of the advanced surface treatment. We experimentally demonstrated surface hardening, amorphizing and alloying with this system. A description of the performance of the system and results of surface treatment experiments are presented. (author)

  13. Can strong-field ionization prepare attosecond dynamics?

    OpenAIRE

    Pabst, Stefan; Wörner, Hans Jakob

    2015-01-01

    Strong-field ionization (SFI) has been shown to prepare wave packets with few-femtosecond periods. Here, we explore whether this technique can be extended to the attosecond time scale. We introduce an intuitive model for predicting the bandwidth of ionic states that can be coherently prepared by SFI. This bandwidth is given by the Fourier-transformed sub-cycle SFI rate and decreases considerably with increasing central wavelength of the ionizing pulse. Many-body calculations based on time-dep...

  14. Cooling of relativistic electron beams in chirped laser pulses

    CERN Document Server

    Yoffe, Samuel R; Kravets, Yevgen; Jaroszynski, Dino A

    2015-01-01

    The next few years will see next-generation high-power laser facilities (such as the Extreme Light Infrastructure) become operational, for which it is important to understand how interaction with intense laser pulses affects the bulk properties of a relativistic electron beam. At such high field intensities, we expect both radiation reaction and quantum effects to play a significant role in the beam dynamics. The resulting reduction in relative energy spread (beam cooling) at the expense of mean beam energy predicted by classical theories of radiation reaction depends only on the energy of the laser pulse. Quantum effects suppress this cooling, with the dynamics additionally sensitive to the distribution of energy within the pulse. Since chirps occur in both the production of high-intensity pulses (CPA) and the propagation of pulses in media, the effect of using chirps to modify the pulse shape has been investigated using a semi-classical extension to the Landau--Lifshitz theory. Results indicate that even la...

  15. Shaping the electron beams with submicrosecond pulse duration in sources and electron accelerators with plasma emitters

    CERN Document Server

    Gushenets, V I

    2001-01-01

    One studies the techniques in use to shape submicrosecond electron beams and the physical processes associated with extraction of electrons from plasma in plasma emitters. Plasma emitter base sources and accelerators enable to generate pulse beams with currents varying from tens of amperes up to 10 sup 3 A, with current densities up to several amperes per a square centimeter, with pulse duration constituting hundreds of nanoseconds and with high frequencies of repetition

  16. Kinetics study of the solvated electron decay in THF using laser-synchronised picosecond electron pulse

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Picosecond pulse radiolysis of neat tetrahydrofuran (THF) shows a fast decay of the solvated electron within 2.5ns. The decay of the solvated electron observed at 790nm is because of spur reaction. A numerical simulation using time dependent Smoluchowski equation containing a sink term with a distance dependent reaction rate is used to fit the pulse-probe data and shows that the geminate reaction can proceed at long distance in this low polar solvent.

  17. The electromagnetic pulse (EMP) as a danger for the world of electronics

    International Nuclear Information System (INIS)

    After discussing the characteristics and formation of a nuclear electromagnetic pulse, the author considers the effects such a pulse would have on various types of electronic systems. Finally he discusses what protection there is against such pulses. (Auth.)

  18. Measuring multimegavolt pulsed voltages using Compton-generated electrons

    Science.gov (United States)

    Swanekamp, S. B.; Weber, B. V.; Pereira, N. R.; Hinshelwood, D. D.; Stephanakis, S. J.; Young, F. C.

    2004-01-01

    The "Compton-Hall" voltmeter is a radiation-based voltage diagnostic that has been developed to measure voltages on high-power (TW) pulsed generators. The instrument collimates photons generated from bremsstrahlung produced in the diode onto an aluminum target to generate Compton-generated electrons. Permanent magnets bend the Compton electron orbits that escape the target toward a silicon pin diode detector. A GaAs photoconductive detector (PCD) detects photons that pass through the Compton target. The diode voltage is determined from the ratio of the electron dose in the pin detector to the x-ray dose in the PCD. The Integrated Tiger Series of electron-photon transport codes is used to determine the relationship between the measured dose ratio and the diode voltage. Variations in the electron beam's angle of incidence on the bremsstrahlung target produce changes in the shape of the photon spectrum that lead to large variations in the voltage inferred from the voltmeter. The voltage uncertainty is minimized when the voltmeter is fielded at an angle of 45° with respect to the bremsstrahlung target. In this position, the photon spectra for different angles of incidence all converge onto a single spectrum reducing the uncertainty in the voltage to less than 10% for voltages below 4 MV. Higher and lower voltages than the range considered in this article can be measured by adjusting the strength of the applied magnetic field or the position of the electron detector relative to the Compton target. The instrument was fielded on the Gamble II pulsed-power generator configured with a plasma opening switch. Measurements produced a time-dependent voltage with a peak (3.7 MV) that agrees with nuclear activation measurements and a pulse shape that is consistent with the measured radiation pulse shape.

  19. Klystron pulse modulator of linear electron accelerator: test results

    Directory of Open Access Journals (Sweden)

    Z. Zimek

    2009-12-01

    Full Text Available Purpose: The purpose of the paper is to describe Klystron pulse modulator of linear electron accelerator.Design/methodology/approach: TH-2158 klystron modulator experimental model is based on semiconductor switch HTS 181-160 FI (acceptable current load 1600 A, and voltage up to 18 kV. The results of test measurements carried out during modulator starting up period are presented in this work. TH-2158 klystron was used as a load. The klystron was connected to the second winding of the pulse HV transformer with 1:10 windings turn ratio. The examined modulator is equipped with safety shutdown circuitry for protection against current overload that may appear at IGBT switch in the case of short-circuiting happened in klystron and waveguide system.Findings: Linear electron accelerator type LAE 10/15 with electron energy 10 MeV and beam power up to 15 kW was designed and completed at Institute of Nuclear Chemistry and Technology. This accelerator was installed in facility for radiation sterilization single use medical devices, implants and tissue grafts. The standing wave accelerating section was selected. Microwave energy used for accelerating process is provided by klystron type TH-2158 working at frequency 2856 MHz.Practical implications: Described HV pulse modulator which designed and constructed for klystron TH-2158 was preliminary tested to evaluate the quality of the klystron HV and load current pulses and optimized selected component parameters. Obtained experimental results are better than those which were predicted by computer simulation method.Originality/value: Description of Klystron pulse modulator of linear electron accelerator.

  20. Relativistic electron accelerations associated with the interplanetary pressure pulse

    Science.gov (United States)

    Miyoshi, Yoshizumi; Saito, Shinji; Matsumoto, Yosuke; Hayashi, Masahiro; Amano, Takanobu; Seki, Kanako

    2016-04-01

    The radiation belt electron fluxes are highly variable, and various time scales for the flux enhancements are observed. The rapid flux enhancements of the outer belt electrons have been observed associated with the solar wind pressure pulse. In order to investigate such rapid flux enhancements, we conduct the code-coupling simulations of GEMSIS-RB test particle simulation [Saito et al., 2010] and GEMSIS-GM global MHD simulation [Matsumoto et al., 2010]. The GEMSIS-RB simulation calculates the 3-dimentional guiding-center motion of a number of test particles in the electric/magnetic fields provided from the GEMSIS-GM. After the arrival of the pressure pulse, the outer belt electrons in the dayside moves inward due to the drift resonance with inductive electric fields of the fast mode waves. Some of electrons are strongly accelerated within a few ten minutes and spiral patterns of drifted electrons can be observed. We may discuss the possibility to identify such selected acceleration of relativistic electrons by Van Allen Probes and upcoming ERG satellite.

  1. Generation of intense pulsed electron beams by the pseudospark discharge

    International Nuclear Information System (INIS)

    A low-pressure gas discharge is presented as a source of intense pulsed electron beams. The so-called pseudospark discharge emits a short-duration pinched electron beam during the breakdown phase. At voltages of typically 20 kV, approximately 10 to 20 percent of the total discharge current appears as the electron beam current of typically 20 ns induration. According to the breakdown voltage in the beam, a power density of the order of 109 W/cm2 is reached. Thus, this electron beam turns out to be a good tool for material processing, comparable to pulsed high-power lasers. Besides the drilling of holes into metals and insulators, an interesting application is the production of high-temperature superconducting thin YBa2Cu3O7-x films. The electron beam is used to evaporate material from a stoichiometric 1-2-3 target. Experimental results concerning the propagation behavior in neutral gas, the electron energy distribution, and the interaction with matter are reported

  2. Femtosecond laser pulse control of electron transfer processes

    Science.gov (United States)

    Mančal, Tomáš; Kleinekathöfer, Ulrich; May, Volkhard

    2002-07-01

    Laser-pulse guided ultrafast electron transfer (ET) is studied theoretically for different types of donor-acceptor systems. The pulse initiates an optical transition from the electronic ground state into an excited state and controls the ET. The computations concentrate on systems where (a) the excited state (donor) is coupled to an acceptor level and where (b) the ET proceeds as an internal conversion from the excited state to the ground state. For both examples the manifold of vibrational coordinates is mapped on a single reaction coordinate coupled to a dissipative reservoir of further coordinates. Utilizing the methods of dissipative quantum dynamics combined with the optimal control (OC) scheme, it is demonstrated that control fields really exist which drive the ET in the required manner. Various properties of the OC algorithm are discussed when applied to dissipative dynamics and a scheme is proposed to avoid pinning in a local extremum.

  3. Pulsed electron source characterization with the modified three gradient method

    CERN Document Server

    Marghitu, S; Dinca, C; Marghitu, O

    2001-01-01

    Results from the Modified Three Gradient Method (MTGM), applied to a pulsed high intensity electron source, are presented. The MTGM makes possible the non-destructive determination of beam emittance in the space charge presence [1]. We apply the MTGM to an experimental system equipped with a Pierce convergent diode, working in pulse mode, and having a directly heated cathode as electron source. This choice was mainly motivated by the availability of an analytical characterization of this source type [2], as well as the extended use of the Pierce type sources in linear accelerators. The experimental data are processed with a numerical matching program, based on the K-V equation for an axially symmetric configuration [3], to determine the emittance and object cross-over position and diameter. The variation of these parameters is further investigated with respect to both electrical and constructive characteristics of the source: cathode heating current, extraction voltage, and cathode-anode distance.

  4. Collective monitors for high-current pulse electron beam diagnostics

    International Nuclear Information System (INIS)

    A collector monitor for high-current pulsed electron beams at average power of 100 W and pulse current of 100 A has been developed. The monitor comprises a Faraday cup, profile monitor, sector diaphragm, energy detector. The collector was fixed on a brass radiator transformed into a rod. The rod ensures reliable and electric contact of the collector with the ''earth'' and small RC of this line. Such design permits to stabilize the heat mode of the collector without utilization of external cooling. The monitors have been tested in electron beams at head load up to 100 W during 40 hours. Wear at the expense of evaporation, microexplosions were not observed. Accuracy of current measuring made up 5-10% for absolute and 1-2% for relative measurements

  5. Multipacting analysis in micro-pulse electron gun

    International Nuclear Information System (INIS)

    Modeling multipacting to steady state saturation is of interest in determining the performance of the micro-pulse electron gun. In this paper, a novel method is proposed to calculate the multipacting resonance parameters for the gun. This method works well, and the 2-D simulation results suggest that steady state saturation can be achieved in the gun. After saturation the transition from two-surface multipacting to single-surface multipacting occurred, and an extensive range of electron emission time is a suggested way to avoid this kind of transition. (authors)

  6. Multistage linear electron acceleration using pulsed transmission lines

    International Nuclear Information System (INIS)

    A four-stage linear electron accelerator is described which uses pulsed radial transmission lines as the basic accelerating units. An annular electron beam produced by a foilless diode is guided through the accelerator by a strong axial magnetic field. Synchronous firing of the injector and the acccelerating modules is accomplished with self-breaking oil switches. The device has accelerated beam currents of 25 kA to kinetic energies of 9 MV, with 90% current transport efficiency. The average accelerating gradient is 3 MV/m

  7. Imaging population transfer in atoms with ultrafast electron pulses

    Science.gov (United States)

    Shao, Hua-Chieh; Starace, Anthony F.

    2016-05-01

    Ultrafast electron diffraction and microscopy have made significant progress recently in investigating atomic-scale structural dynamics in gas-phase and condensed materials. With these advances, direct imaging of electronic motions in atoms and molecules by ultrafast electron diffraction is anticipated. We propose imaging a laser-driven coherent population transfer in lithium atoms by femtosecond ultrafast electron pulses. Valuable information and insight can be obtained from studying such a system in order to refine ultrafast electron techniques and to interpret experimental results. Adiabatic passage by level crossing is used to transfer the electron population from the 2 s to the 2 p state. Our simulations demonstrate the ability of ultrafast electron diffraction to image this population transfer, as the time-dependent diffraction images reflect the electronic motion in the scattering intensity and angular distribution. Furthermore, asymmetric diffraction patterns indicate that even the relative phases of the electronic wave function can be resolved, provided there is sufficient temporal resolution. This work has been supported in part by DOE Award No. DE-SC0012193 [H.-C.S.] and by NSF Grant No. PHYS-1505492 [A.F.S.].

  8. Light-matter interaction on the attosecond timescale

    CERN Document Server

    Dahlström, J M; Maquet, A

    2012-01-01

    This tutorial presents an introduction to the interaction of light and matter on the attosecond timescale. Our aim is to detail the theoretical description of ultra-short time-delays, and to relate these to the phase of extreme ultraviolet (XUV) light pulses and to the asymptotic phase-shifts of photoelectron wave packets. Special emphasis is laid on time-delay experiments, where attosecond XUV pulses are used to photoionize target atoms at well-defined times, followed by a probing process in real time by a phase-locked, infrared laser field. In this way, the laser field serves as a "clock" to monitor the ionization event, but the observable delays do not correspond directly to the delay associated with single-photon ionization. Instead, a significant part of the observed delay originates from a measurement induced process, which obscures the single-photon ionization dynamics. This artifact is traced back to a phase-shift of the above-threshold ionization transition matrix element, which we call the continuum...

  9. Femtosecond single-electron diffraction

    Directory of Open Access Journals (Sweden)

    S. Lahme

    2014-05-01

    Full Text Available Ultrafast electron diffraction allows the tracking of atomic motion in real time, but space charge effects within dense electron packets are a problem for temporal resolution. Here, we report on time-resolved pump-probe diffraction using femtosecond single-electron pulses that are free from intra-pulse Coulomb interactions over the entire trajectory from the source to the detector. Sufficient average electron current is achieved at repetition rates of hundreds of kHz. Thermal load on the sample is avoided by minimizing the pump-probe area and by maximizing heat diffusion. Time-resolved diffraction from fibrous graphite polycrystals reveals coherent acoustic phonons in a nanometer-thick grain ensemble with a signal-to-noise level comparable to conventional multi-electron experiments. These results demonstrate the feasibility of pump-probe diffraction in the single-electron regime, where simulations indicate compressibility of the pulses down to few-femtosecond and attosecond duration.

  10. Study of attosecond delays using perturbation diagrams and exterior complex scaling

    CERN Document Server

    Dahlström, J M

    2014-01-01

    We describe in detail how attosecond delays in laser-assisted photoionization can be computed using perturbation theory based on two-photon matrix elements. Special emphasis is laid on above-threshold ionization, where the electron interacts with an infrared field after photoionization by an extreme ultraviolet field. Correlation effects are introduced using diagrammatic many-body theory to the level of the random-phase approximation with exchange (RPAE). Our aim is to provide an ab initio route to correlated multi-photon processes that are required for an accurate description of experiments on the attosecond time scale. Here, our results are focused on photoionization of the M -shell of argon atoms, where experiments have been carried out using the so-called RABITT technique. An influence of autoionizing resonances in attosecond delay measurements is observed. Further, it is shown that the delay depends on both detection angle of the photoelectron and energy of the probe photon.

  11. Infrared imaging diagnostics for intense pulsed electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Xiao; Shen, Jie; Liu, Wenbin; Zhong, Haowen; Zhang, Jie; Zhang, Gaolong; Le, Xiaoyun, E-mail: xyle@buaa.edu.cn [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); International Research Center for Nuclei and Particles in the Cosmos, Beihang University, Beijing 100191 (China); Qu, Miao; Yan, Sha [Institute of Heavy Ion Physics, Peking University, Beijing 100871 (China)

    2015-08-15

    Infrared imaging diagnostic method for two-dimensional calorimetric diagnostics has been developed for intense pulsed electron beam (IPEB). By using a 100-μm-thick tungsten film as the infrared heat sink for IPEB, the emitting uniformity of the electron source can be analyzed to evaluate the efficiency and stability of the diode system. Two-dimensional axisymmetric finite element method heat transfer simulation, combined with Monte Carlo calculation, was performed for error estimation and optimization of the method. The test of the method was finished with IPEB generated by explosive emission electron diode with pulse duration (FWHM) of 80 ns, electron energy up to 450 keV, and a total beam current of over 1 kA. The results showed that it is possible to measure the cross-sectional energy density distribution of IPEB with energy sensitivity of 0.1 J/cm{sup 2} and spatial resolution of 1 mm. The technical details, such as irradiation protection of bremsstrahlung γ photons and the functional extensibility of the method were discussed in this work.

  12. Mapping Ultrafast Dynamics of Highly Excited H2by Attosecond VUV-Radiation

    Science.gov (United States)

    Weber, Thorsten; Sturm, Felix; Wright, Travis; Ray, Dipanwita; Shivaram, Niranjan; Slaughter, Daniel; Bocharova, Irina; Ranitovic, Predrag; Belkacem, Ali

    2016-05-01

    We show how attosecond vacuum ultraviolet (VUV) and femtosecond infrared (IR) radiation can be used to excite and map dynamics of a highly excited neutral hydrogen molecule. By using time-delayed, strong laser pulses and ion imaging, we map the dynamics of highly-excited, bound states of hydrogen molecules. Due to the large stretching amplitude of the B electronic state, excited by the 9th harmonic of the fundamental laser frequency, the effective ionization potential of the hydrogen molecular ion changes substantially as the nuclear wave packet (NWP) vibrates in the bound, B potential energy curve. Therefore, the probability of ionizing the neutrally-excited hydrogen molecule by the IR probe pulse changes as the NWP evolves in the B potential. We probe this dynamics by ionizing the vibrating molecule by means of time-delayed IR radiation, and identify the dissociation channels with 3D-momentum ion imaging. Supported by DOE under Contract No. DE-AC02-05CH11231.

  13. Chirped pulse inverse free-electron laser vacuum accelerator

    Science.gov (United States)

    Hartemann, Frederic V.; Baldis, Hector A.; Landahl, Eric C.

    2002-01-01

    A chirped pulse inverse free-electron laser (IFEL) vacuum accelerator for high gradient laser acceleration in vacuum. By the use of an ultrashort (femtosecond), ultrahigh intensity chirped laser pulse both the IFEL interaction bandwidth and accelerating gradient are increased, thus yielding large gains in a compact system. In addition, the IFEL resonance condition can be maintained throughout the interaction region by using a chirped drive laser wave. In addition, diffraction can be alleviated by taking advantage of the laser optical bandwidth with negative dispersion focusing optics to produce a chromatic line focus. The combination of these features results in a compact, efficient vacuum laser accelerator which finds many applications including high energy physics, compact table-top laser accelerator for medical imaging and therapy, material science, and basic physics.

  14. Transporting Rydberg Electron Wave Packets with Chirped Trains of Pulses

    International Nuclear Information System (INIS)

    A protocol for steering Rydberg electrons towards targeted final states is realized with the aid of a chirped train of half-cycle pulses (HCPs). Its novel capabilities are demonstrated experimentally by transporting potassium atoms excited to the lowest-lying quasi-one-dimensional states in the ni=350 Stark manifold to a narrow range of much higher-n states. We demonstrate that this coherent state transfer is, to a high degree, reversible. The protocol allows for remarkable selectivity and is highly efficient, with typically over 80% of the parent atoms surviving the HCP sequence

  15. Mode-Locking in a Free-Electron Laser Amplifier

    OpenAIRE

    Thompson, N. R.; McNeil, B.W.J.

    2008-01-01

    A technique is proposed to generate attosecond pulse trains of radiation from a Free-Electron Laser amplifier. The optics-free technique synthesises a comb of longitudinal modes by applying a series of spatio-temporal shifts between the co-propagating radiation and electron bunch in the FEL. The modes may be phase-locked by modulating the electron beam energy at the mode spacing frequency. Three-dimensional simulations demonstrate the generation of a train of 400as pulses at giga-watt power l...

  16. Time-resolved electron density and electron temperature measurements in nanosecond pulse discharges in helium

    Science.gov (United States)

    Roettgen, A.; Shkurenkov, I.; Simeni Simeni, M.; Petrishchev, V.; Adamovich, I. V.; Lempert, W. R.

    2016-10-01

    Thomson scattering is used to study temporal evolution of electron density and electron temperature in nanosecond pulse discharges in helium sustained in two different configurations, (i) diffuse filament discharge between two spherical electrodes, and (ii) surface discharge over plane quartz surface. In the diffuse filament discharge, the experimental results are compared with the predictions of a 2D plasma fluid model. Electron densities are put on an absolute scale using pure rotational Raman spectra in nitrogen, taken without the plasma, for calibration. In the diffuse filament discharge, electron density and electron temperature increase rapidly after breakdown, peaking at n e  ≈  3.5 · 1015 cm-3 and T e  ≈  4.0 eV. After the primary discharge pulse, both electron density and electron temperature decrease (to n e ~ 1014 cm-3 over ~1 µs and to T e ~ 0.5 eV over ~200 ns), with a brief transient rise produced by the secondary discharge pulse. At the present conditions, the dominant recombination mechanism is dissociative recombination of electrons with molecular ions, \\text{He}2+ . In the afterglow, the electron temperature does not relax to gas temperature, due to superelastic collisions. Electron energy distribution functions (EEDFs) inferred from the Thomson scattering spectra are nearly Maxwellian, which is expected at high ionization fractions, when the shape of EEDF is controlled primarily by electron-electron collisions. The kinetic model predictions agree well with the temporal trends detected in the experiment, although peak electron temperature and electron density are overpredicted. Heavy species temperature predicted during the discharge and the early afterglow remains low and does not exceed T  =  400 K, due to relatively slow quenching of metastable He* atoms in two-body and three-body processes. In the surface discharge, peak electron density and electron temperature are n e  ≈  3 · 1014 cm3 and T e

  17. Obtaining precise electron swarm parameters from a pulsed Townsend setup

    Science.gov (United States)

    Dahl, Dominik A.; Teich, Timm H.; Franck, Christian M.

    2012-12-01

    A swarm parameter experiment is introduced, which implements the pulsed Townsend (PT) electrical method with a high degree of automatization. The experimental setup and measurement procedures are described in detail, and a comprehensive definition of the swarm model is given and used for signal analysis. The intrinsic parameters of electron drift currents in the PT method are identified, and novel regression methods are presented for obtaining electron swarm parameters from PT measurements. The setup and methods are verified with measurements in Ar, N2 and CO2, which are focused on the (E/N)-range between dominating electron attachment and weakly dominating ionization. The present data are compared with experimental reference data, and to electron transport coefficients calculated by a Boltzmann solver and simulated by a Monte Carlo method. Excellent agreement was found between the present data and the Monte Carlo results, but there are significant discrepancies to widely used recommended swarm parameters of N2 and CO2. Finally, it is proposed to revise some hitherto recommended values of electron transport coefficients.

  18. Sub-20-Attosecond Timing Jitter Mode-Locked Fiber Lasers

    CERN Document Server

    Kim, Hyoji; Song, Youjian; Yang, Heewon; Shin, Junho; Kim, Chur; Jung, Kwangyun; Wang, Chingyue; Kim, Jungwon

    2014-01-01

    We demonstrate 14.3-attosecond timing jitter [integrated from 10 kHz to 94 MHz offset frequency] optical pulse trains from 188-MHz repetition-rate mode-locked Yb-fiber lasers. In order to minimize the timing jitter, we shorten the non-gain fiber length to shorten the pulsewidth and reduce excessive higher-order nonlinearity and nonlinear chirp in the fiber laser. The measured jitter spectrum is limited by the amplified spontaneous emission limited quantum noise in the 100 kHz - 1 MHz offset frequency range, while it was limited by the relative intensity noise-converted jitter in the lower offset frequency range. This intrinsically low timing jitter enables sub-100-attosecond synchronization between the two mode-locked Yb-fiber lasers over the full Nyquist frequency with a modest 10-kHz locking bandwidth. The demonstrated performance is the lowest timing jitter measured from any free-running mode-locked fiber lasers, comparable to the performance of the lowest-jitter Ti:sapphire solid-state lasers.

  19. The birth of attosecond physics and its coming of age

    Science.gov (United States)

    Krausz, Ferenc

    2016-06-01

    Classical electromagnetism allows the rapidity of light field oscillations to be inferred from measurement of the speed and wavelength of light. Quantum mechanics connects the rapidity of electronic motion with the energy spacing of the occupied quantum states, accessible by light absorption and emission. According to these indirect measurements, both dynamics, the oscillation of light waves as well as electron wavepackets, evolve within attoseconds. With the birth of attosecond metrology at the dawn of the new millennium, light waving and atomic-scale electronic motion, being mutually the cause of each other, became directly measurable. These elementary motions constitute the primary steps of any change in the physical, chemical, and biological properties of materials and living organisms. The capability of observing them is therefore relevant for the development of new materials and technologies, as well as understanding biological function and malfunction. Here, I look back at milestones along the rocky path to the emergence of this capability, with some details about those my group had the chance to make some contributions to. This is an attempt to show—from a personal perspective—how revolution in science or technology now relies on progress at a multitude of fronts, which—in turn—depend on the collaboration of researchers from disparate fields just as on their perseverance.

  20. Two electron response to an intense x-ray free electron laser pulse

    Science.gov (United States)

    Moore, L. R.; Parker, J. S.; Meharg, K. J.; Armstrong, G. S. J.; Taylor, K. T.

    2009-11-01

    New x-ray free electron lasers (FELs) promise an ultra-fast ultra-intense regime in which new physical phenomena, such as double core hole formation in at atom, should become directly observable. Ahead of x-ray FEL experiments, an initial key task is to theoretically explore such fundamental laser-atom interactions and processes. To study the response of a two-electron positive ion to an intense x-ray FEL pulse, our theoretical approach is a direct numerical integration, incorporating non-dipole Hamiltonian terms, of the full six-dimensional time-dependent Schroedinger equation. We present probabilities of double K-shell ionization in the two-electron positive ions Ne8+ and Ar16+ exposed to x-ray FEL pulses with frequencies in the range 50 au to 300 au and intensities in the range 1017 to 1022 W/cm2.

  1. The synthesis of polymer nano hydrogels using pulsed electron beams

    International Nuclear Information System (INIS)

    Complete text of publication follows. Nano-hydrogels made of bio-compatible hydrophilic polymers can be used in various medical applications such as drug delivery and imaging. Intravenously introduced hydrogel-drug conjugate (10 - 200 nm particles can be effectively accumulated in tissues/organs by prolonged circulation and can be selectively transported into tumor tissues by the EPR (enhanced permeability and retention) effect. We are investigating the radiation-induced synthesis of functionalized polymer nano-hydrogels that can serve as targeted nano-medicine carriers. The latest results on the synthesis and kinetic analysis of poly(vinyl pyrrolidone) (PVP) nanogels in dilute aqueous solutions using rays and electron beams, particularly at high temperature, will be presented. At temperatures above 60 deg C, PVP chains start to collapse decreasing its average hydrodynamic radius, Rh from 23 (at 20 deg C) to 15.6 nm (at 80 deg C) due to the disruption of polymer-water hydrogen bonds. The collapsed form of the PVP molecules enhances the intra-crosslinking reactions of the radiolytically produced free radicals leading to a further decrease in its average Rh to the value of 14 nm (γ-ray irradiation with 10 kGy). The nano-gel structure was also synthesized using pulsed electron beam irradiation at high repetition rates, which give rise to a high intra-chain yield of multiple free radicals. These free radicals enhance the intra-crosslinking reactions leading to the formation of smaller size nanogel molecules with average Rh value of 12 nm at 300 pulses per second. At high pulse repetition rates, the intramolecular crosslinking reactions of the carbon centered free radicals are preferred; this effect is enhanced at higher temperatures. While the high dose rate pulses enhance the intra-molecular crosslinking, low dose rate pulses and the extended shape of the PVP molecules favor inter-molecular crosslinking. From the pulse radiolysis, the second order reaction rate

  2. Measurement of Hot Electron Spectrum During the Interaction of Ultrashort Pulse UV Laser With Solid Target

    Institute of Scientific and Technical Information of China (English)

    LIYe-jun; SHANYu-sheng; ZHANGJi; ZHANGHai-feng; TANGXiu-zhang; WANGLei-jian

    2003-01-01

    The hot electron spectrum was measured using electron magnetic spectrometer through the irradiation of solid Cu target by an intense, UV (248 nm) femtosecond (440 fs) laser pulse with free pre-pulse, and the intensity of laser is 1017 W/cm2. We find the electron spectrum presents two temperatures Maxwellian distribution.

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

    Science.gov (United States)

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

    2015-06-01

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

  4. Attosecond Coherent Control of Single and Double Photoionization in Argon.

    Science.gov (United States)

    Hogle, C W; Tong, X M; Martin, L; Murnane, M M; Kapteyn, H C; Ranitovic, P

    2015-10-23

    Ultrafast high harmonic beams provide new opportunities for coherently controlling excitation and ionization processes in atoms, molecules, and materials on attosecond time scales by employing multiphoton two-pathway electron-wave-packet quantum interferences. Here we use spectrally tailored and frequency tuned vacuum and extreme ultraviolet harmonic combs, together with two phase-locked infrared laser fields, to show how the total single and double photoionization yields of argon can be coherently modulated by controlling the relative phases of both optical and electronic-wave-packet quantum interferences. This Letter is the first to apply quantum control techniques to double photoionization, which is a fundamental process where a single, high-energy photon ionizes two electrons simultaneously from an atom. PMID:26551112

  5. Study of attosecond delays using perturbation diagrams and exterior complex scaling

    International Nuclear Information System (INIS)

    We describe in detail how attosecond delays in laser-assisted photoionization can be computed using perturbation theory based on two-photon matrix elements. Special emphasis is laid on above-threshold ionization, where the electron interacts with an infrared field after photoionization by an extreme ultraviolet field. Correlation effects are introduced using diagrammatic many-body theory to the level of the random-phase approximation with exchange. Our aim is to provide an ab initio route to correlated multi-photon processes that are required for an accurate description of experiments on the attosecond time scale. Here, our results are focused on photoionization of the M-shell of argon atoms, where experiments have been carried out using the so-called reconstruction of attosecond beating by the two-photon interference transitions technique. An influence of autoionizing resonances in attosecond delay measurements is observed. Further, it is shown that the delay depends on both detection angle of the photoelectron and energy of the probe photon. (paper)

  6. Deconfinement of Quarks with TeV Attosecond Photon Beams

    Science.gov (United States)

    Stefan, V. Alexander

    2010-02-01

    Recently, I have proposed a novel heuristic method for the deconfinement of quarks.footnotetextM. Gell-Mann. The Quark and the Jaguar: Adventures in the Simple and the Complex (New York, NY: W.H. Freeman and Co., 1994) [cf. M. Gell-Mann, The Garden of Live Flowers in: V. Stefan (Editor), Physics and Society. Essays Honoring Victor Frederick Weisskopf (Springer, 1998), pp. 109-121]. It proceeds in two phases.footnotetextV. Alexander Stefan, On a Heuristic Point of View About Inertial Deconfinement of Quarks, American Physical Society, 2009 APS April Meeting, May 2-5, 2009, abstract #E1.038. Firstly, a frozen hydrogen pellet is inertially confined by the ultra-intense lasers up to a solid state density. Secondly, a solid state nano-pellet is ``punched'' by the photon beam created in the beat wave driven free electron laser (BW-FEL), leading to the ``rapture'' (in a ``karate chop'' model) of the ``MIT Bag''footnotetextJ. I. Friedman and H. Kendall, Viki, in: V. Stefan (Editor), Physics and Society. (Springer, 1998), pp. 103-108]. before the asymptotically free quarks move apart. Hereby, I propose TeV, a few 100s attosecond, photon beams in interaction with the nano-pellet. The threshold ``rapture force'' of the TeV attosecond photon is 10^7 N. )

  7. A 20 kV, 5 A, 1 ns Risetime Pulsed Electron Beam Source

    Institute of Scientific and Technical Information of China (English)

    Chen Yulan; Zeng Zhengzhong; Wang Haiyang; Ma Lianying

    2005-01-01

    A 20 kV, 1 ns risetime pulsed electron beam source was developed using an extremely small gap (0.1 mm) diode driven by a sub-nanosecond risetime, 10 kV rectangular pulse generator. A beam current of 5 A was detected by using a fast response Faraday cup at a distance of 2 cm away from a grid anode. The shot to shot variation of the electron beam pulse was less than 10%.

  8. A 20 kV, 5 A, 1 ns Risetime Pulsed Electron Beam Source

    International Nuclear Information System (INIS)

    A 20 kV, 1 ns risetime pulsed electron beam source was developed using an extremely small gap (0.1 mm) diode driven by a sub-nanosecond risetime, 10 kV rectangular pulse generator. A beam current of 5 A was detected by using a fast response Faraday cup at a distance of 2 cm away from a grid anode. The shot to shot variation of the electron beam pulse was less than 10%

  9. Pulse height measurements and electron attachment in drift chambers operated with Xe,CO2 mixtures

    CERN Document Server

    Andronic, A

    2003-01-01

    We present pulse height measurements in drift chambers operated with Xe,CO2 gas mixtures. We investigate the attachment of primary electrons on oxygen and SF6 contaminants in the detection gas. The measurements are compared with simulations of properties of drifting electrons. We present two methods to check the gas quality: gas chromatography and Fe55 pulse height measurements using monitor detectors.

  10. Two-pulse injector experiments with the RIIM electron accelerator

    International Nuclear Information System (INIS)

    The RADLAC-II accelerator foilless diode injector was operated under double-pulse conditions utilizing the RIIM accelerator as the test bed [M. G. Mazarakis, D. L. Smith, R. B. Miller, R. S. Clark, D. E. Hasti, D. L. Johnson, J. W. Poukey, K. R. Prestwich, and S. L. Shope, IEEE Trans. Nucl. Sci. NS-32, 3237 (1985)]. The original RIIM accelerator pulsed-power network was modified to provide for the generation, transmission, and delivery to the foilless diode of two distinct multimegavolt pulses with variable interpulse separation from 0 to 2 ms. The foilless diode successfully produced two 10-kA current pulses with interpulse separations up to 1 μs. For larger separations, the generated plasma and an excessive neutral gas release following the first pulse prevented the diode from producing a second current pulse

  11. Instantaneous nonvertical electronic transitions with shaped femtosecond laser pulses: Is it possible?

    DEFF Research Database (Denmark)

    Henriksen, Niels Engholm; Møller, Klaus Braagaard

    2003-01-01

    In molecular electronic transitions, a vertical transition can be induced by an ultrashort laser pulse. That is, a replica of the initial nuclear state-times the transition dipole moment of the electronic transition-can be created instantaneously (on the time scale of nuclear motion) in the excited...... electronic state. Now, applying pulse shaping via the modulation of the phases of each spectral component of an ultrashort pulse, it is tempting to ask whether it is also possible to induce instantaneous nonvertical transitions to bound electronic states, provided that the phases of each spectral component...

  12. Evidence of secondary electron emission during PIII pulses as measured by calorimetric probe

    Science.gov (United States)

    Haase, Fabian; Manova, Darina; Mändl, Stephan; Kersten, Holger

    2016-09-01

    Secondary electrons are an ubiquitous nuisance during plasma immersion ion implantation (PIII) necessitating excessive current supplies and shielding for X-rays generated by them. However, additional effects - especially at low pulse voltages - can include interactions with the plasma and transient increases in the plasma density. Here, it is shown that the transient thermal flux associated with secondary electrons emitted from the pulsed substrate can be directly measured using a passive calorimetric probe mounted near the chamber wall away from the pulsed substrate holder. A small increase of a directed energy flux from the substrate towards the probe is consistently observed on top of the isotropic flux from the plasma surrounding the probe, scaling with pulse frequency, pulse voltage, pulse length - as well as depending on gas and substrate material. A strong correlation between voltage and substrate-probe distance is observed, which should allow further investigation of low energy electrons with the plasma itself.

  13. Acceleration of Initially Moving Electrons by a Copropagation Intense Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    JING Guo-Liang; YU Wei; LI Ying-Jun; SENECHA Vinod; CHEN Zhao-Yang; LEI An-Le

    2008-01-01

    Acceleration of an initially moving electron by a copropagation ultra-short ultra-intense laser pulse in vacuum is studied. It is shown that when appropriate laser pulse parameters and focusing conditions are imposed, the acceleration of electron by ascending front of laser pulse can be much stronger compared to the deceleration by descending part. Consequently, the electron can obtain significantly high net energy gain. We also report the results of the new scheme that enables a second-step acceleration of electron using laser pulses of peak intensity in the range of 1019 - 1020 Wμm2/cm2. In the first step the electron acceleration from rest is limited to energies of a few MeV, while in the second step the electron acceleration can be considerably enhanced to about 100 MeV energy.

  14. A new design for a high-voltage pulsed electron gun

    International Nuclear Information System (INIS)

    Characterization of a very simple pulsed electron gun operating in the tens of keV range is presented. Electron emission is based on laser-produced plasma and electrostatic acceleration, generating a homogeneous beam of circular cross section. Electron bunches up to 0.5 nC in 20 ns pulses with 10 mA peak intensity were observed. A continuous energy spectrum was measured and analyzed. (technical design note)

  15. The chirped-pulse free-electron laser: Final technical report, September 1987--October 1988

    International Nuclear Information System (INIS)

    This is the final report of a theoretical and numerical investigation into the operation of pulsed free-electron lasers in which the electron energy depends on the time of injection into the wiggler. Such energy ''chirping'' over each of a train of electron micropulses injected into an FEL oscillator is expected to give rise to a laser pulse inside the optical resonator with a chirped carrier frequency ω/sub s/(/tau/)

  16. Pulse-periodic generation of supershort avalanche electron beams and X-ray emission

    Science.gov (United States)

    Baksht, E. Kh.; Burachenko, A. G.; Erofeev, M. V.; Tarasenko, V. F.

    2014-05-01

    Pulse-periodic generation of supershort avalanche electron beams (SAEBs) and X-ray emission in nitrogen, as well as the transition from a single-pulse mode to a pulse-periodic mode with a high repetition frequency, was studied experimentally. It is shown that, in the pulse-periodic mode, the full width at halfmaximum of the SAEB is larger and the decrease rate of the gap voltage is lower than those in the single-pulse mode. It is found that, when the front duration of the voltage pulse at a nitrogen pressure of 90 Torr decreases from 2.5 to 0.3 ns, the X-ray exposure dose in the pulse-periodic mode increases by more than one order of magnitude and the number of SAEB electrons also increases. It is shown that, in the pulse-periodic mode of a diffuse discharge, gas heating in the discharge gap results in a severalfold increase in the SAEB amplitude (the number of electrons in the beam). At a generator voltage of 25 kV, nitrogen pressure of 90 Torr, and pulse repetition frequency of 3.5 kHz, a runaway electron beam was detected behind the anode foil.

  17. Injection of electrons by colliding laser pulses in a laser wakefield accelerator

    Science.gov (United States)

    Hansson, M.; Aurand, B.; Ekerfelt, H.; Persson, A.; Lundh, O.

    2016-09-01

    To improve the stability and reproducibility of laser wakefield accelerators and to allow for future applications, controlling the injection of electrons is of great importance. This allows us to control the amount of charge in the beams of accelerated electrons and final energy of the electrons. Results are presented from a recent experiment on controlled injection using the scheme of colliding pulses and performed using the Lund multi-terawatt laser. Each laser pulse is split into two parts close to the interaction point. The main pulse is focused on a 2 mm diameter gas jet to drive a nonlinear plasma wave below threshold for self-trapping. The second pulse, containing only a fraction of the total laser energy, is focused to collide with the main pulse in the gas jet under an angle of 150°. Beams of accelerated electrons with low divergence and small energy spread are produced using this set-up. Control over the amount of accelerated charge is achieved by rotating the plane of polarization of the second pulse in relation to the main pulse. Furthermore, the peak energy of the electrons in the beams is controlled by moving the collision point along the optical axis of the main pulse, and thereby changing the acceleration length in the plasma.

  18. Evolution of electron beam pulses of short duration in the solar corona

    Science.gov (United States)

    Casillas-Pérez, G. A.; Jeyakumar, S.; Pérez-Enríquez, H. R.; Trinidad, M. A.

    2016-11-01

    Narrowband radio bursts with durations of the order of milliseconds, called spikes, are known to be associated with solar flares. In order to understand the particle beams responsible for the radio spike phenomena, evolution of electron beam pulses injected from a solar flare region into the corona is studied. Numerical integration of the Fokker-Planck (FP) equation is used to follow the evolution of the electron beam pulse. The simulations show that the short duration pulses lose most of their energy within a second of propagation into the corona. Electron beam with a small low energy cut off is thermalized faster than that with a high low energy cut off.

  19. Evolution of electron beam pulses of short duration in the solar corona

    CERN Document Server

    Casillas-Pérez, G A; Pérez-Enríquez, H R; Trinidad, M A

    2016-01-01

    Narrowband radio bursts with durations of the order of milliseconds, called spikes, are known to be associated with solar flares. In order to understand the particle beams responsible for the radio spike phenomena, evolution of electron beam pulses injected from a solar flare region into the corona is studied. Numerical integration of the Fokker-Planck (FP) equation is used to follow the evolution of the electron beam pulse. The simulations show that the short duration pulses lose most of their energy within a second of propagation into the corona. Electron beam with a small low energy cut off is thermalised faster than that with a high low energy cut off.

  20. Femtosecond pulse radiolysis study of solvation process of electrons in alcohol

    International Nuclear Information System (INIS)

    The solvation processes of electrons in neat n-alcohols have been studied by using the femtosecond pulse radiolysis. The transient optical absorptions of the solvated electrons and the pre-solvated electrons were observed in the visible region and the infrared region, respectively. The reaction rate constants of a dry electron and a pre-solvated electron were obtained by using electron scavengers. The data suggested a dry electron has much higher reactivity than a pre-solvated electron or a solvated electron. (author)

  1. Solid-state pulse modulator using Marx generator for a medical linac electron-gun

    Science.gov (United States)

    Lim, Heuijin; Hyeok Jeong, Dong; Lee, Manwoo; Lee, Mujin; Yi, Jungyu; Yang, Kwangmo; Ro, Sung Chae

    2016-04-01

    A medical linac is used for the cancer treatment and consists of an accelerating column, waveguide components, a magnetron, an electron-gun, a pulse modulator, and an irradiation system. The pulse modulator based on hydrogen thyratron-switched pulse-forming network is commonly used in linac. As the improvement of the high power semiconductors in switching speed, voltage rating, and current rating, an insulated gate bipolar transistor has become the more popular device used for pulsed power systems. We propose a solid-state pulse modulator to generator high voltage by multi-stacked storage-switch stages based on the Marx generator. The advantage of our modulator comes from the use of two semiconductors to control charging and discharging of the storage capacitor at each stage and it allows to generate the pulse with various amplitudes, widths, and shapes. In addition, a gate driver for two semiconductors is designed to reduce the control channels and to protect the circuits. It is developed for providing the pulsed power to a medical linac electron-gun that requires 25 kV and 1 A as the first application. In order to improve the power efficiency and achieve the compactness modulator, a capacitor charging power supply, a Marx pulse generator, and an electron-gun heater isolated transformer are constructed and integrated. This technology is also being developed to extend the high power pulsed system with > 1 MW and also other applications such as a plasma immersed ion implantation and a micro pulse electrostatic precipitator which especially require variable pulse shape and high repetition rate > 1 kHz. The paper describes the design features and the construction of this solid-state pulse modulator. Also shown are the performance results into the linac electron-gun.

  2. Solid-state pulse modulator using Marx generator for a medical linac electron-gun

    International Nuclear Information System (INIS)

    A medical linac is used for the cancer treatment and consists of an accelerating column, waveguide components, a magnetron, an electron-gun, a pulse modulator, and an irradiation system. The pulse modulator based on hydrogen thyratron-switched pulse-forming network is commonly used in linac. As the improvement of the high power semiconductors in switching speed, voltage rating, and current rating, an insulated gate bipolar transistor has become the more popular device used for pulsed power systems. We propose a solid-state pulse modulator to generator high voltage by multi-stacked storage-switch stages based on the Marx generator. The advantage of our modulator comes from the use of two semiconductors to control charging and discharging of the storage capacitor at each stage and it allows to generate the pulse with various amplitudes, widths, and shapes. In addition, a gate driver for two semiconductors is designed to reduce the control channels and to protect the circuits. It is developed for providing the pulsed power to a medical linac electron-gun that requires 25 kV and 1 A as the first application. In order to improve the power efficiency and achieve the compactness modulator, a capacitor charging power supply, a Marx pulse generator, and an electron-gun heater isolated transformer are constructed and integrated. This technology is also being developed to extend the high power pulsed system with > 1 MW and also other applications such as a plasma immersed ion implantation and a micro pulse electrostatic precipitator which especially require variable pulse shape and high repetition rate > 1 kHz. The paper describes the design features and the construction of this solid-state pulse modulator. Also shown are the performance results into the linac electron-gun

  3. Generation of ultrashort radiation pulses by injection locking a regenerative free-electron-laser amplifier

    International Nuclear Information System (INIS)

    We demonstrate how a steady-state train of ultrashort radiation pulses can be produced utilizing a new free-electron laser (FEL) configuration, the injection-locked regenerative klystron amplifier (IRKA). This configuration consists of two elements: (1) a prebuncher, which microbunches the electron beams at the desired output wavelength, and (2) a multipass FEL operated at a very small cavity desynchronism and below the lasing threshold, in the regime of regenerative amplification. The regenerative amplifier is driven by the microbunched electron beam, so that the pulse-to-pulse stability is provided by the pre-buncher. The broad amplification bandwidth of this regenerative amplifier enables generation of ultrashort pulses, much shorter than a slippage length, with high efficiency. The IRKA configuration can produce such ultra-short radiation pulses while avoiding the chaotic dynamics that limits conventional FEL performance. copyright 1997 The American Physical Society

  4. Forward acceleration and generation of femtosecond, megaelectronvolt electron beams by an ultrafast intense laser pulse

    Institute of Scientific and Technical Information of China (English)

    Xiaofang wang(王晓方); Quandong Wang(汪权东); Baifei Shen(沈百飞)

    2003-01-01

    We present a new mechanism of energy gain of electrons accelerated by a laser pulse. It is shown that when the intensity of an ultrafast intense laser pulse decreases rapidly along the direction of propagation, electrons leaving the pulse experience an action of ponderomotive deceleration at the descending part of a lower-intensity laser field than acceleration at the ascending part of a high-intensity field, thus gain net energy from the pulse and move directly forward. By means of such a mechanism, a megaelectronvolt electron beam with a bunch length shorter than 100 fs could be realized with an ultrafast (≤30 fs),intense (>1019 W/cm2) laser pulse.

  5. Simulations and Measurement of Electron Energy and Effective Electron Temperature of Nanosecond Pulsed Argon Plasma%Simulations and Measurement of Electron Energy and Effective Electron Temperature of Nanosecond Pulsed Argon Plasma

    Institute of Scientific and Technical Information of China (English)

    闻雪晴; 信裕; 冯春雷; 丁洪斌

    2012-01-01

    The behavior of argon plasma driven by nanosecond pulsed plasma in a low-pressure plasma reactor is investigated using a global model, and the results are compared with the experimental measurements. The time evolution of plasma density and the electron energy probability function are calculated by solving the energy balance and Boltzmann equations. During and shortly after the discharge pulse, the electron energy probability function can be represented by a bi-Maxwellian distribution, indicating two energy groups of electrons. According to the effective electron temperature calculation, we find that there are more high-energy electrons that play an important role in the excitation and ionization processes than low-energy electrons. The effective electron temperature is also measured via optical emission spectroscopy to evaluate the simulation model. In the comparison, the simulation results are found to be in agreement with the measure- ments. Furthermore, variations of the effective electron temperature are presented versus other discharge parameters, such as pulse width time, pulse rise time and gas pressure.

  6. Pulse-by-pulse multi-beam-line operation for x-ray free-electron lasers

    Science.gov (United States)

    Hara, Toru; Fukami, Kenji; Inagaki, Takahiro; Kawaguchi, Hideaki; Kinjo, Ryota; Kondo, Chikara; Otake, Yuji; Tajiri, Yasuyuki; Takebe, Hideki; Togawa, Kazuaki; Yoshino, Tatsuya; Tanaka, Hitoshi; Ishikawa, Tetsuya

    2016-02-01

    The parallel operation of plural undulator beam lines is an important means of improving the efficiency and usability of x-ray free-electron laser facilities. After the installation of a second undulator beam line (BL2) at SPring-8 Angstrom compact free-electron laser (SACLA), pulse-by-pulse switching between two beam lines was tested using kicker and dc twin-septum magnets. To maintain a compact size, all undulator beam lines at SACLA are designed to be placed within the same undulator hall located downstream of the accelerator. In order to ensure broad tunability of the laser wavelength, the electron bunches are accelerated to different beam energies optimized for the wavelengths of each beam line. In the demonstration, the 30 Hz electron beam was alternately deflected to two beam lines and simultaneous lasing was achieved with 15 Hz at each beam line. Since the electron beam was deflected twice by 3° in a dogleg to BL2, the coherent synchrotron radiation (CSR) effects became non-negligible. Currently in a wavelength range of 4-10 keV, a laser pulse energy of 100 - 150 μ J can be obtained with a reduced peak current of around 1 kA by alleviating the CSR effects. This paper reports the results and operational issues related to the multi-beam-line operation of SACLA.

  7. High energy electron generation by the 15 mJ ultrashort pulse laser

    Energy Technology Data Exchange (ETDEWEB)

    Takano, K; Hotta, E; Nemoto, K [Department of Energy Sciences Tokyo Institute of Technology 4259 Nagatsuta-cho Midori-ku Yokohama 226-8502 (Japan); Nayuki, T; Oishi, Y; Fujii, T; Zhidkov, A [Central Research Institute of Electric Power Industry 2-6-1 Nagasaka, Yokosuka, Kanagawa, 240-0196 (Japan); Todoriki, M; Hasegawa, S [University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8654 (Japan)], E-mail: k-tn@plasma.es.titech.ac.jp

    2008-05-01

    We propose a small size high energy X-ray source utilizing ultrashort pulse lasers, and a new scheme for generating quasi-monoenergetic electrons. In this paper, we developed a compact laser electron generator and performed experiment that generated energetic electrons over 1 MeV electrons with only 15 mJ laser energy. The temperatures of emitted electrons were measured to be 0.2 MeV and 0.25 MeV without and with prepulse, respectively.

  8. A short-current-pulse generator for control of electron gun

    International Nuclear Information System (INIS)

    A setup is described for controlling the current of a triode electron gun. The setup allows shaping of electron pulses with an electron energy of 5-30 keV and a duration of 0.6 to 10 μsec at a repetition frequency of 1 Hz-30 kHz. 3 refs., 2 figs

  9. Attosecond delay of xenon 4 d photoionization at the giant resonance and Cooper minimum

    Science.gov (United States)

    Magrakvelidze, Maia; Madjet, Mohamed El-Amine; Chakraborty, Himadri S.

    2016-07-01

    A Kohn-Sham time-dependent local-density-functional scheme is utilized to predict attosecond time delays of xenon 4 d photoionization that involves the 4 d giant dipole resonance and Cooper minimum. The fundamental effect of electron correlations to uniquely determine the delay at both regions is demonstrated. In particular, for the giant dipole resonance, the delay underpins strong collective effect, emulating the recent prediction at C60 giant plasmon resonance [T. Barillot et al., Phys. Rev. A 91, 033413 (2015), 10.1103/PhysRevA.91.033413]. For the Cooper minimum, a qualitative similarity with a photorecombination experiment near argon 3 p minimum [S. B. Schoun et al., Phys. Rev. Lett. 112, 153001 (2014), 10.1103/PhysRevLett.112.153001] is found. The result should encourage attosecond measurements of Xe 4 d photoemission.

  10. Electronically driven adsorbate excitation mechanism in femtosecond-pulse laser desorption

    DEFF Research Database (Denmark)

    Brandbyge, Mads; Hedegård, Per; Heinz, T. F.;

    1995-01-01

    Femtosecond-pulse laser desorption is a process in which desorption is driven by a subpicosecond temperature pulse of order 5000 K in the substrate-adsorbate electron system, whose energy is transferred into the adsorbate center-of-mass degrees of freedom by a direct coupling mechanism. We presen...

  11. Tilted femtosecond pulses for velocity matching in gas-phase ultrafast electron diffraction

    International Nuclear Information System (INIS)

    Recent advances in pulsed electron gun technology have resulted in femtosecond electron pulses becoming available for ultrafast electron diffraction experiments. For experiments investigating chemical dynamics in the gas phase, the resolution is still limited to picosecond time scales due to the velocity mismatch between laser and electron pulses. Tilted laser pulses can be used for velocity matching, but thus far this has not been demonstrated over an extended target in a diffraction setting. We demonstrate an optical configuration to deliver high-intensity laser pulses with a tilted pulse front for velocity matching over the typical length of a gas jet. A laser pulse is diffracted from a grating to introduce angular dispersion, and the grating surface is imaged on the target using large demagnification. The laser pulse duration and tilt angle were measured at and near the image plane using two different techniques: second harmonic cross correlation and an interferometric method. We found that a temporal resolution on the order of 100 fs can be achieved over a range of approximately 1 mm around the image plane. (paper)

  12. Ion recombination correction for very high dose-per-pulse high-energy electron beams

    International Nuclear Information System (INIS)

    The parallel-plate ionization chamber is the recommended tool for the absorbed dose measurement in pulsed high-energy electron beams. Typically, the electron beams used in radiotherapy have a dose-per-pulse value less then 0.1 cGy/pulse. In this range the factor to correct the response of an ionization chamber for the lack of complete charge collection due to ion recombination (ksat) can be properly evaluated with the standard 'two voltage' method proposed by the international dosimetric reports. Very high dose-per-pulse electron beams are employed in some special Linac dedicated to the Intra-Operatory-Radiation-Therapy (IORT). The high dose-per-pulse values (3-13 cGy/pulse) characterizing the IORT electron beams allow to deliver the therapeutic dose (10-20 Gy) in less than a minute. This considerably reduces the IORT procedure time, but some dosimetric problems arise because the standard method to evaluate ksat overestimates its value by 20%. Moreover, if the dose-per-pulse value >1 cGy/pulse, the dependence of ksat on the dose-per-pulse value cannot be neglected for relative dosimetry. In this work the dependence of ksat on the dose-per-pulse value is derived, based on the general equation that describes the ion recombination in the Boag theory. A new equation for ksat, depending on known or measurable quantities, is presented. The new ksat equation is experimentally tested by comparing the absorbed doses to water measured with parallel-plate ionization chambers (Roos and Markus) to that measured using dose-per-pulse independent dosimeters, such as radiochromic films and chemical Fricke dosimeters. These measurements are performed in the high dose-per-pulse (3-13 cGy/pulse) electron beams of the IORT dedicated Linac Hitesys Novac7 (Aprilia--Latina, Italy). The dose measurements made using the parallel-plate chambers and those made using the dose-per-pulse independent dosimeters are in good agreement (1 cGy/pulse) electron-beam dosimetry

  13. Direct measurement of the electron density of extended femtosecond laser pulse-induced filaments

    OpenAIRE

    Chen, Y.-H.; S. Varma; Antonsen, T. M.; Milchberg, H. M.

    2010-01-01

    We present direct time- and space- resolved measurements of the electron density of femtosecond laser pulse-induced plasma filaments. The dominant nonlinearity responsible for extended atmospheric filaments is shown to be field-induced rotation of air molecules.

  14. Effect of Pulse Width and Fluence of Femtosecond Laser on Electron-Phonon Relaxation Time

    Institute of Scientific and Technical Information of China (English)

    FANG Ran-Ran; ZHANG Duan-Ming; WEI Hua; LI Zhi-Hua; YANG Feng-Xia; TAN Xin-Yu

    2008-01-01

    The electron-phonon relaxation time as functions of pulse width and fluence of femtosecond laser is studied based on the two-temperature model. The two-temperature model is solved using a finite difference method for copper target. The temperature distribution of the electron and the lattice along with space and time for a certain laser fluence is presented. The time-dependence of lattice and electron temperature of the surface for different pulse width and different laser fluence are also performed, respectively. Moreover, the variation of heat-affected zone per pulse with laser fluence is obtained. The satisfactory agreement between our numerical results and experimental data indicates that the electron-phonon relaxation time is reasonably accurate with the influences of pulse width and fluence of femtosecond laser.

  15. Design of light Ⅱ-B pulsed power electron accelerator

    International Nuclear Information System (INIS)

    The Light Ⅱ-B was built at the side of the Marx tank of Light Ⅱ-A for X-pinch test, which kept the original capacity of KrF excimer laser, and can be used for relevant researches of X-pinch. It is composed of a Marx generator, a pulse forming line (PFL), a gas-filled switch, a pulse transmission line (PTL), and a copper-sulphate resistive load. The medium of the forming line is deionized water. The input impendence of the pulse forming line is 6 Ω, corresponding to an output impendence of 1.25 Ω for the pulse transfer line. The design of circuit simulation and the debugging results in resistance load were introduced. The results show that the current peak load is about 269 kA, pulse width is about 50 ns, and the current rise tune is less than 30 ns when the load is 1.25 Ω. It indicates that Light Ⅱ-B has the ability to drive low impedance X-pinch experimental line. (authors)

  16. Attosecond nonlinear polarization and light-matter energy transfer in solids.

    Science.gov (United States)

    Sommer, A; Bothschafter, E M; Sato, S A; Jakubeit, C; Latka, T; Razskazovskaya, O; Fattahi, H; Jobst, M; Schweinberger, W; Shirvanyan, V; Yakovlev, V S; Kienberger, R; Yabana, K; Karpowicz, N; Schultze, M; Krausz, F

    2016-05-23

    Electric-field-induced charge separation (polarization) is the most fundamental manifestation of the interaction of light with matter and a phenomenon of great technological relevance. Nonlinear optical polarization produces coherent radiation in spectral ranges inaccessible by lasers and constitutes the key to ultimate-speed signal manipulation. Terahertz techniques have provided experimental access to this important observable up to frequencies of several terahertz. Here we demonstrate that attosecond metrology extends the resolution to petahertz frequencies of visible light. Attosecond polarization spectroscopy allows measurement of the response of the electronic system of silica to strong (more than one volt per ångström) few-cycle optical (about 750 nanometres) fields. Our proof-of-concept study provides time-resolved insight into the attosecond nonlinear polarization and the light-matter energy transfer dynamics behind the optical Kerr effect and multi-photon absorption. Timing the nonlinear polarization relative to the driving laser electric field with sub-30-attosecond accuracy yields direct quantitative access to both the reversible and irreversible energy exchange between visible-infrared light and electrons. Quantitative determination of dissipation within a signal manipulation cycle of only a few femtoseconds duration (by measurement and ab initio calculation) reveals the feasibility of dielectric optical switching at clock rates above 100 terahertz. The observed sub-femtosecond rise of energy transfer from the field to the material (for a peak electric field strength exceeding 2.5 volts per ångström) in turn indicates the viability of petahertz-bandwidth metrology with a solid-state device.

  17. Attosecond nonlinear polarization and light-matter energy transfer in solids.

    Science.gov (United States)

    Sommer, A; Bothschafter, E M; Sato, S A; Jakubeit, C; Latka, T; Razskazovskaya, O; Fattahi, H; Jobst, M; Schweinberger, W; Shirvanyan, V; Yakovlev, V S; Kienberger, R; Yabana, K; Karpowicz, N; Schultze, M; Krausz, F

    2016-06-01

    Electric-field-induced charge separation (polarization) is the most fundamental manifestation of the interaction of light with matter and a phenomenon of great technological relevance. Nonlinear optical polarization produces coherent radiation in spectral ranges inaccessible by lasers and constitutes the key to ultimate-speed signal manipulation. Terahertz techniques have provided experimental access to this important observable up to frequencies of several terahertz. Here we demonstrate that attosecond metrology extends the resolution to petahertz frequencies of visible light. Attosecond polarization spectroscopy allows measurement of the response of the electronic system of silica to strong (more than one volt per ångström) few-cycle optical (about 750 nanometres) fields. Our proof-of-concept study provides time-resolved insight into the attosecond nonlinear polarization and the light-matter energy transfer dynamics behind the optical Kerr effect and multi-photon absorption. Timing the nonlinear polarization relative to the driving laser electric field with sub-30-attosecond accuracy yields direct quantitative access to both the reversible and irreversible energy exchange between visible-infrared light and electrons. Quantitative determination of dissipation within a signal manipulation cycle of only a few femtoseconds duration (by measurement and ab initio calculation) reveals the feasibility of dielectric optical switching at clock rates above 100 terahertz. The observed sub-femtosecond rise of energy transfer from the field to the material (for a peak electric field strength exceeding 2.5 volts per ångström) in turn indicates the viability of petahertz-bandwidth metrology with a solid-state device. PMID:27251280

  18. Attosecond nonlinear polarization and light-matter energy transfer in solids

    Science.gov (United States)

    Sommer, A.; Bothschafter, E. M.; Sato, S. A.; Jakubeit, C.; Latka, T.; Razskazovskaya, O.; Fattahi, H.; Jobst, M.; Schweinberger, W.; Shirvanyan, V.; Yakovlev, V. S.; Kienberger, R.; Yabana, K.; Karpowicz, N.; Schultze, M.; Krausz, F.

    2016-06-01

    Electric-field-induced charge separation (polarization) is the most fundamental manifestation of the interaction of light with matter and a phenomenon of great technological relevance. Nonlinear optical polarization produces coherent radiation in spectral ranges inaccessible by lasers and constitutes the key to ultimate-speed signal manipulation. Terahertz techniques have provided experimental access to this important observable up to frequencies of several terahertz. Here we demonstrate that attosecond metrology extends the resolution to petahertz frequencies of visible light. Attosecond polarization spectroscopy allows measurement of the response of the electronic system of silica to strong (more than one volt per ångström) few-cycle optical (about 750 nanometres) fields. Our proof-of-concept study provides time-resolved insight into the attosecond nonlinear polarization and the light-matter energy transfer dynamics behind the optical Kerr effect and multi-photon absorption. Timing the nonlinear polarization relative to the driving laser electric field with sub-30-attosecond accuracy yields direct quantitative access to both the reversible and irreversible energy exchange between visible-infrared light and electrons. Quantitative determination of dissipation within a signal manipulation cycle of only a few femtoseconds duration (by measurement and ab initio calculation) reveals the feasibility of dielectric optical switching at clock rates above 100 terahertz. The observed sub-femtosecond rise of energy transfer from the field to the material (for a peak electric field strength exceeding 2.5 volts per ångström) in turn indicates the viability of petahertz-bandwidth metrology with a solid-state device.

  19. Further Acceleration of MeV Electrons by a Relativistic Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    HE Feng; YU Wei; LU Pei-Xiang; XU Han; SHEN Bai-Fei; QIAN Lie-Jia; LI Ru-Xin; XU Zhi-Zhan

    2005-01-01

    With the development of photocathode rf electron gun, electrons with high-brightness and mono-energy can be obtained easily. By numerically solving the relativistic equations of motion of an electron generated from this facility in laser fields modelled by a circular polarized Gaussian laser pulse, we find the electron can obtain high energy gain from the laser pulse. The corresponding acceleration distance for this electron driven by the ascending part of the laser pulse is much longer than the Rayleigh length, and the light amplitude experienced on the electron is very weak when the laser pulse overtakes the electron. The electron is accelerated effectively and the deceleration can be neglected.For intensities around 1019 W·μm2/cm2,an electron's energy gain near 0.1 GeV can be realized when its initial energy is 4.5 MeV, and the final velocity of the energetic electron is parallel with the propagation axis. The energy gain can be up to 1 GeV if the intensity is about 1021 W·μm2/cm2.The final energy gain of the electron as a function of its initial conditions and the parameters of the laser beam has also been discussed.

  20. The design of an electron gun grid pulse circuit for a single bunch mode operation

    International Nuclear Information System (INIS)

    Siam Photon Source (Thailand) operates multiple bunch system at Booster. For the single bunch mode operation, the electron gun will emit a bunch of electron at pulse width 4 ns. A gun grid circuit is designed by using a pulse forming network and an avalanche technique. The circuit is tested with a high bandwidth oscilloscope and the circuit is then connected to the gun assembly.

  1. Low-temperature radiation cracking of heavy oil under continuous and pulse electron irradiation

    Science.gov (United States)

    Zaikin, Yuriy A.

    2016-05-01

    The dependence of the chain reaction parameters on the conditions of pulse and continuous electron irradiation is analyzed for the case of low-temperature radiation cracking of heavy oils. The specificity of kinetics and yields of light products after radiation cracking are considered in the cases of continuous and pulse irradiation. Theoretical calculations are compared with experimental data on electron irradiation of heavy oil in different conditions.

  2. Device for the removal of sulfur dioxide from exhaust gas by pulsed energization of free electrons

    International Nuclear Information System (INIS)

    The performance of a new device using pulsed streamer corona for the removal of sulfur dioxide from humid air has been evaluated. The pulsed streamer corona produced free electrons which enhance gas-phase chemical reactions, and convert SO2 to sulfuric acid mist. The SO2 removal efficiency was compared with that of the electron-beam flue-gas treatment process. The comparison demonstrates the advantage of the novel device

  3. 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.

  4. On the response of electronic personal dosimeters in constant potential and pulsed X-ray beams

    Energy Technology Data Exchange (ETDEWEB)

    Guimaraes, Margarete C.; Silva, Teogenes; Silva, Claudete R.E., E-mail: margaretecristinag@gmail.com [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Oliveira, Paulo Marcio C. de [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Anatomia e Imagem

    2015-07-01

    Electronic personal dosimeters (EPDs) based on solid state detectors have widely been used but some deficiencies in their response in pulsed radiation beams have been reported. Nowadays, there is not an international standard for pulsed X-ray beams for calibration or type testing of dosimeters. Irradiation conditions for testing the response of EPDs in both the constant potential and pulsed X-ray beams were established in CDTN. Three different types of EPDs were tested in different conditions in similar ISO and IEC X-ray qualities. Results stressed the need of performing additional checks before using EPDs in constant potential or pulsed X-rays. (author)

  5. Ultrashort electron pulses as a four-dimensional diagnosis of plasma dynamics.

    Science.gov (United States)

    Zhu, P F; Zhang, Z C; Chen, L; Li, R Z; Li, J J; Wang, X; Cao, J M; Sheng, Z M; Zhang, J

    2010-10-01

    We report an ultrafast electron imaging system for real-time examination of ultrafast plasma dynamics in four dimensions. It consists of a femtosecond pulsed electron gun and a two-dimensional single electron detector. The device has an unprecedented capability of acquiring a high-quality shadowgraph image with a single ultrashort electron pulse, thus permitting the measurement of irreversible processes using a single-shot scheme. In a prototype experiment of laser-induced plasma of a metal target under moderate pump intensity, we demonstrated its unique capability of acquiring high-quality shadowgraph images on a micron scale with a-few-picosecond time resolution. PMID:21034089

  6. Ultrashort electron pulses as a four-dimensional diagnosis of plasma dynamics

    International Nuclear Information System (INIS)

    We report an ultrafast electron imaging system for real-time examination of ultrafast plasma dynamics in four dimensions. It consists of a femtosecond pulsed electron gun and a two-dimensional single electron detector. The device has an unprecedented capability of acquiring a high-quality shadowgraph image with a single ultrashort electron pulse, thus permitting the measurement of irreversible processes using a single-shot scheme. In a prototype experiment of laser-induced plasma of a metal target under moderate pump intensity, we demonstrated its unique capability of acquiring high-quality shadowgraph images on a micron scale with a-few-picosecond time resolution.

  7. Effect of high-energy electrons component on recombination plasma with pulse plasma flow

    International Nuclear Information System (INIS)

    Experiments on a recombination plasma with pulse plasma flow have been performed in the linear divertor simulator TPD-SheetIV. The pulse plasma flow was generated using a switching circuit controlled by the electric potential of the adjacent floating electrode in the plasma source. The duration of the pulse was 0.3 ms at a frequency of 50 Hz. The time dependence of the electron density ne, temperature Te, and energy distribution function fe(E) were measured using a Langmuir probe. The ionization and recombination events are analyzed using the Collisional-Radiative model, taking into account high-energy electrons. (author)

  8. Simulation of the relativistic electron dynamics and acceleration in a linearly-chirped laser pulse

    CERN Document Server

    Jisrawi, Najeh M; Salamin, Yousef I

    2014-01-01

    Theoretical investigations are presented, and their results are discussed, of the laser acceleration of a single electron by a chirped pulse. Fields of the pulse are modeled by simple plane-wave oscillations and a $\\cos^2$ envelope. The dynamics emerge from analytic and numerical solutions to the relativistic Lorentz-Newton equations of motion of the electron in the fields of the pulse. All simulations have been carried out by independent Mathematica and Python codes, with identical results. Configurations of acceleration from a position of rest as well as from injection, axially and sideways, at initial relativistic speeds are studied.

  9. A sub-picosecond pulsed 5 MeV electron beam system

    International Nuclear Information System (INIS)

    Laser excited pulsed, electron beam systems that operate at energies from 1 MeV up to 5 MeV and pulse width from 0.1 to 100 ps are described. The systems consist of a high voltage pulser and a coaxial laser triggered gas or liquid spark gap. The spark gap discharges into a pulse forming line designed to produce and maintain a flat voltage pulse for 1 ns duration on the cathode of a photodiode. A synchronized laser is used to illuminate the photocathode with a laser pulse to produce an electron beam with very high brightness, short duration, and current at or near the space charge limit. Operation of the system is described and preliminary test measurements of voltages, synchronization, and jitter are presented for a 5 MeV system. Applications in chemistry, and accelerator research are briefly discussed

  10. A perspective on novel sources of ultrashort electron and X-ray pulses

    International Nuclear Information System (INIS)

    Graphical abstract: In this perspective, we discuss the performances of modern X-FEL and pulsed electrons sources; in particular, we focus our attention on diffraction from solids and molecules and we describe the advantages and disadvantages of the different approaches in terms of spatial resolution, temporal resolution, coherence and damage induced in the specimen. We describe also an approach that combines ultrafast X-rays and electron pulses for performing innovative experiments on materials, taking advantage of the potential of both technologies. The aim of this perspective is to evidence the great potential of modern ultrafast technology, both X-rays and electron based, and their complementarity.▪ Highlights: ► We compare ultrafast X-rays and electron pulses for imaging diffraction and spectroscopy. ► Modern electron technology is a valid complement to more expensive X-ray tools. ► We propose a novel approach that combines X-rays pump and electron probing for material science. - Abstract: Recently, much attention has been devoted to the development of new pulsed sources of radiation for investigating matter with atomic scale temporal and spatial resolution. While much has been achieved thanks to modern ultrafast laser technology, the ultimate coherent light source, the X-ray free electron laser (X-FEL), promises to deliver the highest X-ray photon flux in the shortest pulses at energies unreachable by conventional solid-state lasers. In parallel, other approaches that utilize electrons in table-top setups as a probe have been developed demonstrating the potential for a valid complement to X-ray based techniques. Here, we consider yet another possible avenue in which the technology of electron diffraction and imaging is pushed further; we estimate the interest and performances of a femtosecond high energy electron microscope and propose a hybrid experiment with relativistic electrons as a probe and fs X-ray pulses as a pump taking advantage of both

  11. Multiple quasi-monoenergetic electron beams from laser-wakefield acceleration with spatially structured laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y.; Li, M. H.; Li, Y. F.; Wang, J. G.; Tao, M. Z.; Han, Y. J.; Zhao, J. R.; Huang, K.; Yan, W. C.; Ma, J. L.; Li, Y. T. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080 (China); Chen, L. M., E-mail: lmchen@iphy.ac.cn [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080 (China); Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Li, D. Z. [Institute of High Energy Physics, CAS, Beijing 100049 (China); Chen, Z. Y. [Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621999 (China); Sheng, Z. M. [Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Zhang, J. [Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-08-15

    By adjusting the focus geometry of a spatially structured laser pulse, single, double, and treble quasi-monoenergetic electron beams were generated, respectively, in laser-wakefield acceleration. Single electron beam was produced as focusing the laser pulse to a single spot. While focusing the laser pulse to two spots that are approximately equal in energy and size and intense enough to form their own filaments, two electron beams were produced. Moreover, with a proper distance between those two focal spots, three electron beams emerged with a certain probability owing to the superposition of the diffractions of those two spots. The energy spectra of the multiple electron beams are quasi-monoenergetic, which are different from that of the large energy spread beams produced due to the longitudinal multiple-injection in the single bubble.

  12. Mode Locking in a Free-Electron Laser Amplifier

    International Nuclear Information System (INIS)

    A technique is proposed to generate attosecond pulse trains of radiation from a free-electron laser amplifier. The optics-free technique synthesizes a comb of longitudinal modes by applying a series of spatiotemporal shifts between the copropagating radiation and electron bunch in the free-electron laser. The modes may be phase locked by modulating the electron beam energy at the mode spacing frequency. Three-dimensional simulations demonstrate the generation of a train of 400 as pulses at gigawatt power levels evenly spaced by 2.5 fs at a wavelength of 124 A ring . In the x-ray at wavelength 1.5 A ring , trains of 23 as pulses evenly spaced by 150 as and of peak power up to 6 GW are predicted

  13. Direct Electron Acceleration with Radially Polarized Laser Beams

    Directory of Open Access Journals (Sweden)

    Michel Piché

    2013-01-01

    Full Text Available In the past years, there has been a growing interest in innovative applications of radially polarized laser beams. Among them, the particular field of laser-driven electron acceleration has received much attention. Recent developments in high-power infrared laser sources at the INRS Advanced Laser Light Source (Varennes, Qc, Canada allowed the experimental observation of a quasi-monoenergetic 23-keV electron beam produced by a radially polarized laser pulse tightly focused into a low density gas. Theoretical analyses suggest that the production of collimated attosecond electron pulses is within reach of the actual technology. Such an ultrashort electron pulse source would be a unique tool for fundamental and applied research. In this paper, we propose an overview of this emerging topic and expose some of the challenges to meet in the future.

  14. Electron Acceleration by a Focused Gaussian Laser Pulse in Vacuum

    Institute of Scientific and Technical Information of China (English)

    何峰; 余玮; 陆培祥; 徐涵

    2004-01-01

    By numerically solving the relativistic equations of motion of a single electron in laser fields modeled by a Gaussian laser beam, we get the trajectory and energy of the electron. When the drifting distance is comparable to or even longer than the corresponding Rayleigh length, the evolution of the beam waist cannot be neglected. The asymmetry of intensity in acceleration and deceleration leads to the conclusion that the electron can be accelerated effectively and extracted by the longitudinal ponderomotive force. For intensities above, an electron's energy gain about MeV can be realized, and the energetic electron is parallel with the propagation axis.

  15. Pulse radiolysis with (sub) nanosecond time resolution using a 3 MV electron accelerator

    International Nuclear Information System (INIS)

    In this thesis the development of equipment for pulse radiolysis is described and the application of the technique to time-resolved measurements of the fluorescence emission of excited states formed after irradiation of some alkanes is dealt with. A review is given of the development of the pulsed 3MV Van de Graaf electron accelerator for the generation of subnanosecond electron beam pulses and of the development of the equipment for optical detection as accomplished by the author. The initial stage of a further development for shorter pulses and higher time resolution is briefly discussed. A collection of papers on the development of apparatus and a collection of papers dealing with the results obtained from measurements of the fluorescence of excited states, formed by the recombination of electrons and ions in irradiated alkanes such as cyclohexane and the decalines, are included. (Auth.)

  16. Measurements of absorbed energy distributions in water from pulsed electron beams

    International Nuclear Information System (INIS)

    An evaluation of the use of a holographic interferometer to measure the energy deposition as a function of depth in water from pulsed electron beams, together with a brief description of the interferometer and the technique of generating a hologram are presented. The holographic interferometer is used to measure the energy deposition as a function of depth in water from various pulsed beams of monoenergetic electrons in the energy range from 1.0 to 2.5 MeV. These results are compared to those computed by using a Monte Carlo radiation transport code, ETRAN-15, for the same electron energies. After the discrepancies between the measured and computed results are evaluated, reasonable agreement is found between the measured and computed absorbed energy distributions as a function of depth in water. An evalutation of the response of the interferometer as a function of electron intensities is performed. A comparison among four energy deposition curves that result from the irradiation of water with pulsed electron beams from a Febetron accelerator, model 705, is presented. These pulsed beams were produced by the same vacuum diode with the same charging voltage. The results indicate that the energy distribution of the electrons in the pulsed beam is not always constant. A comparison of the energy deposition curves that result from the irradiation of water with electron pulses from different vacuum diodes but the same charging voltage is presented. These results indicate again that the energy distribution of the electrons in the pulsed beam may vary between vacuum diodes. These differences would not be realized by using a totally absorbing metal calorimeter and Faraday Cup

  17. Laser Activated Streak Camera for Measurement of Electron Pulses with Femtosecond Resolution

    Science.gov (United States)

    Zandi, Omid; Desimone, Alice; Wilkin, Kyle; Yang, Jie; Centurion, Martin

    2015-05-01

    The duration of femtosecond electron pulses used in time-resolved diffraction and microscopy experiments is challenging to measure in-situ. To overcome this problem, we have fabricated a streak camera that uses the time-varying electric field of a discharging parallel plate capacitor. The capacitor is discharged using a laser-activated GaAs photoswitch, resulting in a damped oscillation of the electric field. The delay time between the laser pulse and electron pulse is set so that the front and back halves of the bunch encounter opposite electric fields of the capacitor and are deflected in opposite directions. Thus, the electron bunch appears streaked on the detector with a length proportional to its duration. The temporal resolution of the streak camera is proportional to the maximum value of the electric field and the frequency of the discharge oscillation. The capacitor is charged by high voltage short pulses to achieve a high electric field and prevent breakdown. We have achieved an oscillation frequency in the GHz range by reducing the circuit size and hence its inductance. The camera was used to measure 100 keV electron pulses with up to a million electrons that are compressed transversely by magnetic lenses and longitudinally by an RF cavity. This work was supported mainly by the Air Force Office of Scientific Research, Ultrashort Pulse Laser Matter Interaction program, under grant # FA9550-12-1-0149.

  18. Global Remote Sensing of Precipitating Electron Energies: A Comparison of Substorms and Pressure Pulse Related Intensifications

    Science.gov (United States)

    Chua, D.; Parks, G. K.; Brittnacher, M. J.; Germany, G. A.; Spann, J. F.

    2000-01-01

    The Polar Ultraviolet Imager (UVI) observes aurora responses to incident solar wind pressure pulses and interplanetary shocks such its those associated with coronal mass ejections. Previous observations have demonstrated that the arrival of it pressure pulse at the front of the magnetosphere results in highly disturbed geomagnetic conditions and a substantial increase in both dayside and nightside aurora precipitations. Our observations show it simultaneous brightening over bread areas of the dayside and nightside auroral in response to a pressure pulse, indicating that more magnetospheric regions participate as sources for auroral precipitation than during isolate substorm. We estimate the characteristic energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated event to those during isolated substorms. We estimate the characteristic energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated events to those during isolated auroral substorms. Electron precipitation during substorms has characteristic energies greater than 10 KeV and is structured both in local time and in magnetic latitude. For auroral intensifications following the arrival of'a pressure pulse or interplanetary shock. Electron precipitation is less spatially structured and has greater flux of lower characteristic energy electrons (Echar less than 7 KeV) than during isolated substorm onsets. These observations quantify the differences between global and local auroral precipitation processes and will provide a valuable experimental check for models of sudden storm commencements and magnetospheric response to perturbations in the solar wind.

  19. Multistart spiral electron vortices in ionization by circularly polarized UV pulses

    Science.gov (United States)

    Ngoko Djiokap, J. M.; Meremianin, A. V.; Manakov, N. L.; Hu, S. X.; Madsen, L. B.; Starace, Anthony F.

    2016-07-01

    Multistart spiral vortex patterns are predicted for the electron momentum distributions in the polarization plane following ionization of the helium atom by two time-delayed circularly polarized ultrashort laser pulses. For two ultraviolet (UV) pulses having the same frequency (such that two photons are required for ionization), single-color two-photon interferometry with corotating or counter-rotating time-delayed pulses is found to lead respectively to zero-start or four-start spiral vortex patterns in the ionized electron momentum distributions in the polarization plane. In contrast, two-color one-photon plus two-photon interferometry with time-delayed corotating or counter-rotating UV pulses is found to lead respectively to one-start or three-start spiral vortex patterns. These predicted multistart electron vortex patterns are found to be sensitive to the carrier frequencies, handedness, time delay, and relative phase of the two pulses. Our numerical predictions are obtained by solving the six-dimensional two-electron time-dependent Schrödinger equation (TDSE). They are explained analytically using perturbation theory (PT). Comparison of our TDSE and PT results for single-color two-photon processes probes the role played by the time-delay-dependent ionization cross channels in which one photon is absorbed from each pulse. Control of these cross channels by means of the parameters of the fields and the ionized electron detection geometries is discussed.

  20. Pulsed high-current electron source: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Spindt, C.A.

    1988-10-01

    The objective of this investigation was to investigate ways to realize the cathode's potential as a source for high power pulse operation. The questions that needed to be studied were those of large area coverage, maximum emission that the cathode arrays are capable of producing practically, uniformity of emission over large areas, and the ability to operate with high voltage anodes. 9 figs.

  1. Relativistic Tennis with Photons: Demonstration of Frequency Upshifting by a Relativistic Flying Mirror through Two Colliding Laser Pulses

    CERN Document Server

    Kando, M; Pirozhkov, A S; Ma, J; Daito, I; Chen, L -M; Esirkepov, T Zh; Ogura, K; Homma, T; Hayashi, Y; Kotaki, H; Sagisaka, A; Mori, M; Koga, J K; Daido, H; Bulanov, S V; Kimura, T; Kato, Y; Tajima, T

    2007-01-01

    Since the advent of chirped pulse amplification1 the peak power of lasers has grown dramatically and opened the new branch of high field science, delivering the focused irradiance, electric fields of which drive electrons into the relativistic regime. In a plasma wake wave generated by such a laser, modulations of the electron density naturally and robustly take the shape of paraboloidal dense shells, separated by evacuated regions, moving almost at the speed of light. When we inject another counter-propagating laser pulse, it is partially reflected from the shells, acting as relativistic flying (semi-transparent) mirrors, producing an extremely time-compressed frequency-multiplied pulse which may be focused tightly to the diffraction limit. This is as if the counterstreaming laser pulse bounces off a relativistically swung tennis racket, turning the ball of the laser photons into another ball of coherent X-ray photons but with a form extremely relativistically compressed to attosecond and zeptosecond levels....

  2. Radiation Reaction Effects in Cascade Scattering of Intense, Tightly Focused Laser Pulses by Relativistic Electrons

    CERN Document Server

    Zhidkov, A; Bulanov, S S; Hosokai, T; Koga, J; Kodama, R

    2013-01-01

    Non-linear cascade scattering of intense, tightly focused laser pulses by relativistic electrons is studied numerically in the classical approximation including the radiation damping for the quantum parameter hwx-ray/E<1 and an arbitrary radiation parameter Kai. The electron energy loss, along with its side scattering by the ponderomotive force, makes the scattering in the vicinity of high laser field nearly impossible at high electron energies. The use of a second, co-propagating laser pulse as a booster is shown to solve this problem.

  3. The Boersch effect in a picosecond pulsed electron beam emitted from a semiconductor photocathode

    Science.gov (United States)

    Kuwahara, Makoto; Nambo, Yoshito; Aoki, Kota; Sameshima, Kensuke; Jin, Xiuguang; Ujihara, Toru; Asano, Hidefumi; Saitoh, Koh; Takeda, Yoshikazu; Tanaka, Nobuo

    2016-07-01

    The space charge effect has been clearly observed in the energy distributions of picosecond pulse beams from a spin-polarized electron microscope, and was found to depend upon the quantity of charge per pulse. The non-linear phenomena associated with this effect have also been replicated in beam simulations that take into account of a three-dimensional space charge. The results show that a charge of 500 aC/pulse provides the highest brightness with a 16-ps pulse duration, a 30-keV beam energy, and an emission spot of 1.8 μm. Furthermore, the degeneracy of the wave packet of the pulsed electron beam has been evaluated to be 1.6 × 10-5 with a charge of 100 aC/pulse, which is higher than that for a continuously emitted electron beam despite the low beam energy of 30 keV. The high degeneracy and high brightness contribute to the realization of high temporal and energy resolutions in low-voltage electron microscopy, which will serve to reduce radiolysis damage and enhance scattering contrast.

  4. Energy-spread measurement of triple-pulse electron beams based on the magnetic dispersion principle

    CERN Document Server

    Wang, Yi; Yang, Zhiyong; Zhang, Huang; Ding, Hengsong; Yang, Anmin; Wang, Minhong

    2016-01-01

    The energy-spread of the triple-pulse electron beam generated by the Dragon-II linear induction accelerator is measured using the method of energy dispersion in the magnetic field. A sector magnet is applied for energy analyzing of the electron beam, which has a bending radius of 300 mm and a deflection angle of 90 degrees. For each pulse, both the time-resolved and the integral images of the electron position at the output port of the bending beam line are recorded by a streak camera and a CCD camera, respectively. Experimental results demonstrate an energy-spread of less than +-2.0% for the electron pulses. The cavity voltage waveforms obtained by different detectors are also analyzed for comparison.

  5. 150 keV intense electron beam accelerator system with high repeated pulse

    International Nuclear Information System (INIS)

    A 150 keV electron beam accelerator system has been developed for wide application of high power particle beams. The new wire-ion-plasma electron gun has been adopted. The parameters are as follows: Output energy - 130-150 keV; Electron beam density - 250 mA/cm2; Pulse duration - 1 μs; Pulse rate 100 pps; Section of electron beam - 5 x 50 cm2. This equipment can be used to study repeated pulse CO2 laser, to be a preionizer of high power discharge excimer laser and to perform radiation curing process, and so on. The first part contains principle and design consideration. Next is a description of experimental arrangement. The remainder is devoted to describing experimental results and its application

  6. Double ionization of a two-electron model atom in a single-cycle laser pulse

    International Nuclear Information System (INIS)

    We present theoretical results from the solution of a widely used model atom containing two interacting electrons in one dimension bound to a soft-Coulomb potential and ionized by an intense, short laser pulse. A half-cycle pulse leads to strong single but no double ionization (down to a probability density of 10-12). A full-cycle laser pulse at low frequency leads to double ionization which begins precisely at the classical return time for the first ejected electron. At weak field, double ionization occurs at the time of maximum return kinetic energy. When the excursion range for the first electron is truncated, the double ionization at later times, corresponding to longer excursions, disappears. When the field near the nucleus is turned off during the return of the first electron, double ionization persists

  7. Ultra-short photon pulse generation in relativistic laser-plasmas

    International Nuclear Information System (INIS)

    Optical pulse compression by the linear reflection of a laser pulse from a relativistically moving plasma is studied. Using Lorentz transformations, covariance of Maxwell's equations and the principle of phase invariance to transform between the rest frame and the moving frame, analytics can be exactly performed in the moving frame. Closed-form formulae for reflected waveforms as a function of incident angle show temporal compression and intensity amplification by a factor of 2γ and 4γ2, respectively, where γ is the Lorentz factor of the relativistic electron plasma. As an independent test, fully relativistic electromagnetic particle simulations agree well with analytical results, predicting pulse compression and large amplification to be of relevance to the generation of attosecond optical pulses. (paper)

  8. Electromagnetic processes in the pulsed inductors of electron accelerators

    Directory of Open Access Journals (Sweden)

    В. Т. Чемерис

    2013-07-01

    Full Text Available The process of magnetic field setting up at its excitation in the cross section of the closed laminated core of the pulsed inductor has been investigated by numerical methods. Analysis of the field expansion from the boundaries of cross section to its center was realized due to using of two-dimensional numerical model of the wave equation written in non-dimensional form with application of equivalent magnetic μ and dielectric ε parameters. Two situations had been taken into consideration: 1 the medium of laminated package has anisotropic ideal magneto-dielectric properties (no electrical conductivity; 2 the medium of package is isotropic, but has the losses of energy due to electrical conductivity of ferromagnetic layers. The ratio  of the basic velocity (which defines via basic dimension of the package cross section and duration of the pulsed field to the speed of electromagnetic wave propagation in this medium  serves as characteristic parameter of similarity for the processes in models with different scale of time and/or dimensions. The magnetic Reynolds’ number  must be used additionally as the measure of the field diffusion. The character of wave processes in the core has been studied and the conditions of their essential influence on the field distribution have been established. That is shown that main criterion for estimation of the core filling up by the magnetic flux (i.e. for estimation of package using effectiveness is the correlation between the dimension of cross section and the path of the wave run during the pulse duration. The criterion for observation only diffusion picture of the field propagation at the magnetic Reynolds’ number is the ratio . Under conditions when the wave phenomena play relatively small role the speed of the field diffusion instead of the velocity of the wave propagation must be used at the estimation of the package cross section effective usage

  9. Electromagnetic cascade in high energy electron, positron, and photon interactions with intense laser pulses

    CERN Document Server

    Bulanov, S S; Esarey, E; Leemans, W P

    2013-01-01

    The interaction of high energy electrons, positrons, and photons with intense laser pulses is studied in head-on collision geometry. It is shown that electrons and/or positrons undergo a cascade-type process involving multiple emissions of photons. These photons can consequently convert into electron-positron pairs. As a result charged particles quickly lose their energy developing an exponentially decaying energy distribution, which suppresses the emission of high energy photons, thus reducing the number of electron-positron pairs being generated. Therefore, this type of interaction suppresses the development of the electromagnetic avalanche-type discharge, i.e., the exponential growth of the number of electrons, positrons, and photons does not occur in the course of interaction. The suppression will occur when 3D effects can be neglected in the transverse particle orbits, i.e., for sufficiently broad laser pulses with intensities that are not too extreme. The final distributions of electrons, positrons, and...

  10. Surface cracking of soda lime glass under pulsed high-current electron radiation

    International Nuclear Information System (INIS)

    Electron beam radiation has been widely used to modify the surface properties of materials such as metals, ceramics, and glasses. However, a few investigations of surface topology of glasses after electron irradiation can be found. In contrast to the surface cracking by bending, indentation, and thermally induced stress in soda lime glasses a 2 μs pulsed high-current electron beam was used to modify the surfaces of soda lime glass. Surface topology of irradiated samples was studied by using traditional optical microscopy and atomic force microscopy. Parallel to and perpendicular to surface cracks were observed. The depth of crack can be obtained by electron penetration, Newton's ring and AFM. The stress to produce the crack by electron radiation was calculated using three obtained depths. The observed surface crack is explained in terms of radiation-induced thermal stress and high local electric field-induced by deposited charges from pulsed electrons

  11. Double ionization effect in electron accelerations by high-intensity laser pulse interaction with a neutral gas

    International Nuclear Information System (INIS)

    We study the effect of laser-induced double-ionization of a helium gas (with inhomogeneous density profile) on vacuum electron acceleration. For enough laser intensity, helium gas can be found doubly ionized and it strengthens the divergence of the pulse. The double ionization of helium gas can defocus the laser pulse significantly, and electrons are accelerated by the front of the laser pulse in vacuum and then decelerated by the defocused trail part of the laser pulse. It is observed that the electrons experience a very low laser-intensity at the trailing part of the laser pulse. Hence, there is not much electron deceleration at the trailing part of the pulse. We found that the inhomogeneity of the neutral gas reduced the rate of tunnel ionization causing less defocusing of the laser pulse and thus the electron energy gain is reduced. (authors)

  12. Multichannel computerized control system of current pulses in LIU-30 electron accelerator

    CERN Document Server

    Gerasimov, A I; Kulgavchuk, V V; Pluzhnikov, A V

    2002-01-01

    In LIU-30 power linear pulsed induction electron accelerator (40 MeV, 10 kA, 25 ns) 288 radial lines with water insulation serve as energy accumulators and shapers of accelerating voltage pulses. The lines are charged simultaneously up to 500 kV using a system comprising 72 Arkadiev-Marx screened generators. To control parameter of synchronous pulses of charging current with up to 60 kA amplitude and 0.85 mu s duration in every of 72 charging circuits one applies a computer-aided system. Current pulse is recorded at output of every generator using the Rogowski coil signal from which via a cable line is transmitted to an analog-digital converter, is processed with 50 ns sampling and is recorded to a memory unit. Upon actuation of accelerator the signals are sequentially or selectively displayed and are compared with pulse typical shape

  13. Multichannel computerized control system of current pulses in LIU-30 electron accelerator

    International Nuclear Information System (INIS)

    In LIU-30 power linear pulsed induction electron accelerator (40 MeV, 10 kA, 25 ns) 288 radial lines with water insulation serve as energy accumulators and shapers of accelerating voltage pulses. The lines are charged simultaneously up to 500 kV using a system comprising 72 Arkadiev-Marx screened generators. To control parameter of synchronous pulses of charging current with up to 60 kA amplitude and 0.85 μs duration in every of 72 charging circuits one applies a computer-aided system. Current pulse is recorded at output of every generator using the Rogowski coil signal from which via a cable line is transmitted to an analog-digital converter, is processed with 50 ns sampling and is recorded to a memory unit. Upon actuation of accelerator the signals are sequentially or selectively displayed and are compared with pulse typical shape

  14. VLF wave stimulation by pulsed electron beams injected from the Space Shuttle

    Science.gov (United States)

    Reeves, G. D.; Banks, P. M.; Frazer-Smith, A. C.; Neubert, T.; Bush, R. I.

    1988-01-01

    Among the investigations conducted on the Space Shuttle flight STS-3 of March 1982 was an experiment in which a 1-keV, 100-mA electron gun was pulsed at 3.25 and 4.87 kHz. The resultant waves were measured with a broadband plasma wave receiver. At the time of flight the experimental setup was unique in that the electron beam was square wave modulated and that the Shuttle offered relatively long times for in situ measurements of the ionospheric plasma response to the VLF pulsing sequences. In addition to electromagnetic response at the pulsing frequencies the wave exhibited various spectral harmonics as well as the unexpected occurrence of 'satellite lines' around those harmonics. Both phenomena occurred with a variety of different characteristics for different pulsing sequences.

  15. Factors Influencing the Electron Yield of Needle-Ring Pulsed Corona Discharge Electron Source for Negative Ion Mobility Spectrometer

    Science.gov (United States)

    Liu, Xin; Li, Shengli; Li, Mingshu

    2013-12-01

    A simple negative ion mobility spectrometer (IMS) is designed and used to investigate the factors that influence the number and efficiency of electrons generated by the needle-ring pulsed corona discharge electron source. Simulation with Ansoft Maxwell 12 is carried out to analyze the electric field distribution within the IMS, and to offer the basis and foundation for analyzing the measurement results. The measurement results of the quantities of electrons show that when the drift electric field strength and the ring inner diameter rise, both the number of effective electrons and the effective electron rate are increased. When the discharge voltage becomes stronger, the number of effective electrons goes up while the effective electron rate goes down. In light of the simulation results, mechanisms underlying the effects of drift electric field strength, ring inner diameter, and discharge voltage on the effective electron number and effective electron rate are discussed. These will make great sense for designing negative ion mode IMS using the needle-ring pulsed corona discharge as the electron source.

  16. Half-period optical pulse generation using a free-electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Jaroszynski, D.A.; Chaix, P.; Piovella, N. [Commissariat a l`Energie Atomique, Bruycres-le-Chatel (France)

    1995-12-31

    Recently there has been growth, in interest in non-equilibrium interaction of half-period long optical pulses with matter. To date the optical pulses have been produced by chopping out a half-period long segment from a longer pulse using a semiconductor switch driven by a femtosecond laser. In this paper we present new methods for producing tunable ultra-short optical pulses as short as half an optical period using a free-electron laser driven by electron bunches with a duration a fraction of an optical period. Two different methods relying on the production of coherent spontaneous emission will be described. In the first method we show that when a train of ultra-short optical pulses as short as one half period. We present calculations which show that the small signal gain is unimportant in the early stages of radiation build up in the cavity when the startup process is dominated by coherent spontaneous emission. To support our proposed method we present encouraging experimental results from the FELIX experiment in the Netherlands which show that interference effects between the coherent spontaneous optical pulses at start-up are very important. The second proposed method relies on the fact that coherent spontaneous emission mimics the undulations of electrons as they pass through the undulator. We show that ultra-short optical pulses are produced by coherent spontaneous emission when ultra-short electron bunches pass through an ultra-short undulator. We discuss the interesting case of such undulator radiation in the presence of an optical cavity and show that the optical pulse can be {open_quotes}taylored{close_quotes} by simply adjusting the optical cavity desynchronism. The proposed methods may be realisable using existing rf driven FELs in the far-infrared.

  17. Mode-Locking in a Free-Electron Laser Amplifier

    CERN Document Server

    Thompson, N R

    2008-01-01

    A technique is proposed to generate attosecond pulse trains of radiation from a Free-Electron Laser amplifier. The optics-free technique synthesises a comb of longitudinal modes by applying a series of spatio-temporal shifts between the co-propagating radiation and electron bunch in the FEL. The modes may be phase-locked by modulating the electron beam energy at the mode spacing frequency. Three-dimensional simulations demonstrate the generation of a train of 400 as pulses at giga-watt power levels evenly spaced by 2.5 fs at a wavelength of 124 angstrom. In the X-ray at wavelength 1.5 angstrom, trains of 23 as pulses evenly spaced by 150 as and of peak power up to 6 GW are predicted.

  18. Damage threshold and focusability of mid-infrared free-electron laser pulses gated by a plasma mirror with nanosecond switching pulses

    CERN Document Server

    Wang, Xiaolong; Zen, Heishun; Kii, Toshiteru; Ohgaki, Hideaki

    2013-01-01

    The presence of a pulse train structure of an oscillator-type free-electron laser (FEL) results in the immediate damage of a solid target upon focusing. We demonstrate that the laser-induced damage threshold can be significantly improved by gating the mid-infrared (MIR) FEL pulses with a plasma mirror. Although the switching pulses we employ have a nanosecond duration which does not guarantee the clean wavefront of the gated FEL pulses, the high focusablity is experimentally confirmed through the observation of spectral broadening by a factor of 2.1 when we tightly focus the gated FEL pulses onto the Ge plate.

  19. Production and application of pulsed slow-positron beam using an electron LINAC

    Energy Technology Data Exchange (ETDEWEB)

    Yamazaki, Tetsuo; Suzuki, Ryoichi; Ohdaira, Toshiyuki; Mikado, Tomohisa [Electrotechnical Lab., Tsukuba, Ibaraki (Japan); Kobayashi, Yoshinori

    1997-03-01

    Slow-positron beam is quite useful for non-destructive material research. At the Electrotechnical Laboratory (ETL), an intense slow positron beam line by exploiting an electron linac has been constructed in order to carry out various experiments on material analysis. The beam line can generates pulsed positron beams of variable energy and of variable pulse period. Many experiments have been carried out so far with the beam line. In this paper, various capability of the intense pulsed positron beam is presented, based on the experience at the ETL, and the prospect for the future is discussed. (author)

  20. Single-shot characterization of independent femtosecond extreme ultraviolet free electron and infrared laser pulses

    International Nuclear Information System (INIS)

    Two-color above threshold ionization of helium and xenon has been used to analyze the synchronization between individual pulses of the femtosecond extreme ultraviolet (XUV) free electron laser in Hamburg and an independent intense 120 fs mode-locked Ti:sapphire laser. Characteristic sidebands appear in the photoelectron spectra when the two pulses overlap spatially and temporally. The cross-correlation curve points to a 250 fs rms jitter between the two sources at the experiment. A more precise determination of the temporal fluctuation between the XUV and infrared pulses is obtained through the analysis of the single-shot sideband intensities

  1. On the analysis of photo-electron spectra

    International Nuclear Information System (INIS)

    We analyze Photo-Electron Spectra (PES) for a variety of excitation mechanisms from a simple mono-frequency laser pulse to involved combination of pulses as used, e.g., in attosecond experiments. In the case of simple pulses, the peaks in PES reflect the occupied single-particle levels in combination with the given laser frequency. This usual, simple rule may badly fail in the case of excitation pulses with mixed frequencies and if resonant modes of the system are significantly excited. We thus develop an extension of the usual rule to cover all possible excitation scenarios, including mixed frequencies in the attosecond regime. We find that the spectral distributions of dipole, monopole and quadrupole power for the given excitation taken together and properly shifted by the single-particle energies provide a pertinent picture of the PES in all situations. This leads to the derivation of a generalized relation allowing to understand photo-electron yields even in complex experimental setups

  2. Peculiarities of profile formation for orifices fabricated by electron beam drilling at gun pulsed supply with trapezoidal voltage

    International Nuclear Information System (INIS)

    Peculiarities of substance removal from the surface of a solid body under effect of a pulse beam with beam diameter varying during the pulse and distribution of power density by its cross section taking place at electron gun pulsed supply with trapezoidal voltage are considered. Conical holes with different configuration of the profile envelope can be obtained with variation of pulse duration. Photos of hole profiles obtained by pulsed beam at gun pulsed supply with different pulse duration are presented. Experiments have been conducted with various materials including quartz and nickel

  3. Probing the structure of the mechanosensitive channel of small conductance in lipid bilayers with pulsed electron-electron double resonance

    OpenAIRE

    Ward, Richard; Pliotas, Christos; Branigan, Emma; Hacker, Christian; Rasmussen, Akiko; Hagelueken, Gregor; Booth, Ian R.; Miller, Samantha; Lucocq, John; Naismith, Jim; Schiemann, Olav

    2014-01-01

    Mechanosensitive channel proteins are important safety valves against osmotic shock in bacteria, and are involved in sensing touch and sound waves in higher organisms. The mechanosensitive channel of small conductance (MscS) has been extensively studied. Pulsed electron-electron double resonance (PELDOR or DEER) of detergent-solubilized protein confirms that as seen in the crystal structure, the outer ring of transmembrane helices do not pack against the pore- forming helices, creating an app...

  4. Electron energy distributions and electron impact source functions in Ar/N2 inductively coupled plasmas using pulsed power

    International Nuclear Information System (INIS)

    In plasma materials processing, such as plasma etching, control of the time-averaged electron energy distributions (EEDs) in the plasma allows for control of the time-averaged electron impact source functions of reactive species in the plasma and their fluxes to surfaces. One potential method for refining the control of EEDs is through the use of pulsed power. Inductively coupled plasmas (ICPs) are attractive for using pulsed power in this manner because the EEDs are dominantly controlled by the ICP power as opposed to the bias power applied to the substrate. In this paper, we discuss results from a computational investigation of EEDs and electron impact source functions in low pressure (5–50 mTorr) ICPs sustained in Ar/N2 for various duty cycles. We find there is an ability to control EEDs, and thus source functions, by pulsing the ICP power, with the greatest variability of the EEDs located within the skin depth of the electromagnetic field. The transit time of hot electrons produced in the skin depth at the onset of pulse power produces a delay in the response of the EEDs as a function of distance from the coils. The choice of ICP pressure has a large impact on the dynamics of the EEDs, whereas duty cycle has a small influence on time-averaged EEDs and source functions

  5. Pulse radiolysis study of solvated electron formation in glassy alcohols at low temperature

    International Nuclear Information System (INIS)

    Pulse radiolysis study of glass-forming alcohols at low temperature (140K∼RT) was carried out to clarify the primary process of pre-solvated and solvated electron in lower alcohols. The very slow decay of pre-solvated electron and the very slow formation of solvated electron were observed at nanosecond region because of very high viscosity of alcohols near melting and glass transition temperature. The activation energy of solvated electron formation was estimated to be 0.17 eV, and this suggests that the formation process of solvated electron depends on a break of hydrogen bond due to reorientation of OH-groups. (author)

  6. Generation of large-bandwidth x-ray free-electron-laser pulses

    Science.gov (United States)

    Saa Hernandez, Angela; Prat, Eduard; Bettoni, Simona; Beutner, Bolko; Reiche, Sven

    2016-09-01

    X-ray free-electron lasers (XFELs) are modern research tools in disciplines such as biology, material science, chemistry, and physics. Besides the standard operation that aims at minimizing the bandwidth of the produced XFEL radiation, there is a strong scientific demand to produce large-bandwidth XFEL pulses for several applications such as nanocrystallography, stimulated Raman spectroscopy, and multiwavelength anomalous diffraction. We present a self-consistent method that maximizes the XFEL pulse bandwidth by systematically maximizing the energy chirp of the electron beam at the undulator entrance. This is achieved by optimizing the compression scheme and the electron distribution at the source in an iterative back-and-forward tracking. Start-to-end numerical simulations show that a relative bandwidth of 3.25% full-width can be achieved for the hard x-ray pulses in the SwissFEL case.

  7. Selective triggering of phase change in dielectrics by femtosecond pulse trains based on electron dynamics control

    Institute of Scientific and Technical Information of China (English)

    Xu Chuan-Cai; Jiang Lan; Leng Ni; Liu Peng-Jun

    2013-01-01

    In this study we experimentally reveal that the phase change mechanism can be selectively triggered by shaping femtosecond pulse trains based on electron dynamics control (EDC),including manipulation of excitations,ionizations,densities,and temperatures of electrons.By designing the pulse energy distribution to adjust the absorptions,excitations,ionizations,and recombinations of electrons,the dominant phase change mechanism experiences transition from nonthermal to thermal process.This phenomenon is observed in quadruple,triple,and double pulses per train ablation of fused silica separately.This opens up possibilities for controlling phase change mechanisms by EDC,which is of great significance in laser processing of dielectrics and fabrication of integrated nano-and micro-optical devices.

  8. Nanosecond pulse-width electron diode based on dielectric wall accelerator technology

    Science.gov (United States)

    Zhao, Quantang; Zhang, Z. M.; Yuan, P.; Cao, S. C.; Shen, X. K.; Jing, Y.; Yu, C. S.; Li, Z. P.; Liu, M.; Xiao, R. Q.; Zong, Y.; Wang, Y. R.; Zhao, H. W.

    2013-11-01

    An electron diode using a short section of dielectric wall accelerator (DWA) has been under development at the Institute of Modern Physics (IMP), Chinese Academy of Sciences. Tests have been carried out with spark gap switches triggered by lasers. The stack voltage efficiency of a four-layer of Blumleins reached about 60-70% with gas filled spark gap switching. The generated pulse voltage of peak amplitude of 23 kV and pulse width of 5 ns is used to extract and accelerate an electron beam of 320 mA, measured by a fast current transformer. A nanosecond pulse width electron diode was achieved successfully. Furthermore, the principle of a DWA is well proven and the development details and discussions are presented in this article.

  9. Electron Beam Energy Compensation by Controlling RF Pulse Shape

    CERN Document Server

    Kii, T; Kusukame, K; Masuda, K; Nakai, Y; Ohgaki, H; Yamazaki, T; Yoshikawa, K; Zen, H

    2005-01-01

    We have studied on improvement of electron beam macropulse properties from a thermionic RF gun. Though a thermionic RF gun has many salient features, there is a serious problem that back-bombardment effect worsens quality of the beam. To reduce beam energy degradation by this effect, we tried to feed non-flat RF power into the gun. As a result, we successfully obtained about 1.5 times longer macropulse and two times larger total charge per macropulse. On the other hand, we calculated transient evolution of RF power considering non-constant beam loading. The beam loading is evaluated from time evolution of cathode temperature, by use of one dimensional heat conduction model and electron trajectories' calculations by a particle simulation code. Then we found good agreement between the experimental and calculation results. Furthermore, with the same way, we studied the electron beam output dependence on the cathode radius.

  10. Optical control of electron phase space in plasma accelerators with incoherently stacked laser pulses

    International Nuclear Information System (INIS)

    It is demonstrated that synthesizing an ultrahigh-bandwidth, negatively chirped laser pulse by incoherently stacking pulses of different wavelengths makes it possible to optimize the process of electron self-injection in a dense, highly dispersive plasma (n0∼1019 cm−3). Avoiding transformation of the driving pulse into a relativistic optical shock maintains a quasi-monoenergetic electron spectrum through electron dephasing and boosts electron energy far beyond the limits suggested by existing scaling laws. In addition, evolution of the accelerating bucket in a plasma channel is shown to produce a background-free, tunable train of femtosecond-duration, 35–100 kA, time-synchronized quasi-monoenergetic electron bunches. The combination of the negative chirp and the channel permits acceleration of electrons beyond 1 GeV in a 3 mm plasma with 1.4 J of laser pulse energy, thus offering the opportunity of high-repetition-rate operation at manageable average laser power

  11. Hot electron production in laser solid interactions with a controlled pre-pulse

    Energy Technology Data Exchange (ETDEWEB)

    Culfa, O.; Tallents, G. J.; Wagenaars, E.; Ridgers, C. P.; Dance, R. J.; Rossall, A. K.; Woolsey, N. C. [York Plasma Institute, Department of Physics, The University of York, York YO10 5DD (United Kingdom); Gray, R. J.; McKenna, P. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Brown, C. D. R.; James, S. F.; Hoarty, D. J. [AWE, Aldermaston, Reading, Berkshire RG7 4PR (United Kingdom); Booth, N.; Robinson, A. P. L. [CLF, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX (United Kingdom); Lancaster, K. L. [York Plasma Institute, Department of Physics, The University of York, York YO10 5DD (United Kingdom); CLF, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX (United Kingdom); Pikuz, S. A. [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412 (Russian Federation); Faenov, A. Ya. [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412 (Russian Federation); Quantum Beam Science Directorate, Japan Atomic Energy Agency, Kizugawa, Kyoto 619-0215 (Japan); Kampfer, T.; Schulze, K. S.; Uschmann, I. [Friedrich Schiller University of Jena, D-07743 Jena (Germany)

    2014-04-15

    Hot electron generation plays an important role in the fast ignition approach to inertial confinement fusion (ICF) and other applications with ultra-intense lasers. Hot electrons of temperature up to 10–20 MeV have been produced by high contrast picosecond duration laser pulses focussed to intensities of ∼10{sup 20} W cm{sup −2} with a deliberate pre-pulse on solid targets using the Vulcan Petawatt Laser facility. We present measurements of the number and temperature of hot electrons obtained using an electron spectrometer. The results are correlated to the density scale length of the plasma produced by a controlled pre-pulse measured using an optical probe diagnostic. 1D simulations predict electron temperature variations with plasma density scale length in agreement with the experiment at shorter plasma scale lengths (<7.5μm), but with the experimental temperatures (13–17 MeV) dropping below the simulation values (20–25 MeV) at longer scale lengths. The experimental results show that longer interaction plasmas produced by pre-pulses enable significantly greater number of hot electrons to be produced.

  12. Interaction of a laser-produced electron beam with an ultra-intense laser pulse

    Science.gov (United States)

    Valenzuela, A. R.; Shah, R. C.; Banerjee, S.; Sepke, S. M.; Maksimchuk, A.; Umstadter, D. P.

    2004-11-01

    We report our latest experimental findings demonstrating the transfer of longitudinal momentum from high-intensity laser light to free electrons in vacuum. Two synchronized laser pulses are used: one to generate an electron beam, and a second, with which to scatter. The acceleration of electrons is through the self-modulated wakefield mechanism that produces electron energies in excess of 1 MeV with a divergence of less than 1 degree. The second laser pulse is focused to a normalized intensity, a0 ˜ 0.4. The longitudinal momentum affects the trajectory of the electrons causing the beam to deflect, in agreement with theoretical models that include the longitudinal fields of a focused Gaussian pulse [1]. Besides its intrinsic relevance to fundamental physics, the effect is also useful both as a diagnostic for measuring the duration of an electron pulse with sub-picosecond resolution and for beam conditioning. [1] B. Quesnel and P. Mora, Phys. Rev. E 58, 3719 (1998). Work supported by DOE, NSF and Sandia National Laboratory.

  13. Nanosecond pulse-width electron diode based on dielectric wall accelerator technology

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Quantang, E-mail: zhaoquantang@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Z.M.; Yuan, P.; Cao, S.C.; Shen, X.K.; Jing, Y. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Yu, C.S. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Li, Z.P.; Liu, M.; Xiao, R.Q. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zong, Y.; Wang, Y.R. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao, H.W. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2013-11-21

    An electron diode using a short section of dielectric wall accelerator (DWA) has been under development at the Institute of Modern Physics (IMP), Chinese Academy of Sciences. Tests have been carried out with spark gap switches triggered by lasers. The stack voltage efficiency of a four-layer of Blumleins reached about 60–70% with gas filled spark gap switching. The generated pulse voltage of peak amplitude of 23 kV and pulse width of 5 ns is used to extract and accelerate an electron beam of 320 mA, measured by a fast current transformer. A nanosecond pulse width electron diode was achieved successfully. Furthermore, the principle of a DWA is well proven and the development details and discussions are presented in this article. -- Highlights: •The key technology of DWA, including switches and pulse forming lines were studied. •The SiC PCSS obtained from Shanghai Institute were tested. •Two layers ZIP lines (new structure) and four layers Blumlein lines were studied with laser triggered spark gap switches. •A nanosecond pulse-width electron diode based on DWA technologies is achieved and studied experimentally. •The principle of DWA is also proved by the diode.

  14. Pulse radiolysis study of reaction of bull serum albumin electron adduct with oxygen. Polychromatic kinetics of reaction with adsorbed oxygen

    International Nuclear Information System (INIS)

    By the method of pulse radiolysis the reaction of bull serum albumin electron adduct with oxygen is investigated. As pulsed radiation source electron linear accelerators with particle energy of 8.0 and 4.5 MeV and pulse time of 40 ns and 2.2 μs, respectively have been used. It is assumed that the disappearance of protein electron adduct occurs in the course of its interaction with oxygen adsorbed on protein globular molecule

  15. Electron beam-based sources of ultrashort x-ray pulses.

    Energy Technology Data Exchange (ETDEWEB)

    Zholents, A.; Accelerator Systems Division (APS)

    2010-09-30

    A review of various methods for generation of ultrashort x-ray pulses using relativistic electron beam from conventional accelerators is presented. Both spontaneous and coherent emission of electrons is considered. The importance of the time-resolved studies of matter at picosecond (ps), femtosecond (fs), and atttosecond (as) time scales using x-rays has been widely recognized including by award of a Nobel Prize in 1999 [Zewa]. Extensive reviews of scientific drivers can be found in [BES1, BES2, BES3, Lawr, Whit]. Several laser-based techniques have been used to generate ultrashort x-ray pulses including laser-driven plasmas [Murn, Alte, Risc, Rose, Zamp], high-order harmonic generation [Schn, Rund, Wang, Arpi], and laser-driven anode sources [Ande]. In addition, ultrafast streak-camera detectors have been applied at synchrotron sources to achieve temporal resolution on the picosecond time scale [Wulf, Lind1]. In this paper, we focus on a different group of techniques that are based on the use of the relativistic electron beam produced in conventional accelerators. In the first part we review several techniques that utilize spontaneous emission of electrons and show how solitary sub-ps x-ray pulses can be obtained at existing storage ring based synchrotron light sources and linacs. In the second part we consider coherent emission of electrons in the free-electron lasers (FELs) and review several techniques for a generation of solitary sub-fs x-ray pulses. Remarkably, the x-ray pulses that can be obtained with the FELs are not only significantly shorter than the ones considered in Part 1, but also carry more photons per pulse by many orders of magnitude.

  16. Experimental Study of Diamond Like Carbon (DLC) Coated Electrodes for Pulsed High Gradient Electron Gun

    CERN Document Server

    Paraliev, M; Ivkovic, S; Le Pimpec, F

    2010-01-01

    For the SwissFEL Free Electron Laser project at the Paul Scherrer Institute, a pulsed High Gradient (HG) electron gun was used to study low emittance electron sources. Different metals and surface treatments for the cathode and anode were studied for their HG suitability. Diamond Like Carbon (DLC) coatings are found to perform exceptionally well for vacuum gap insulation. A set of DLC coated electrodes with different coating parameters were tested for both vacuum breakdown and photo electron emission. Surface electric fields over 250MV/m (350 - 400kV, pulsed) were achieved without breakdown. From the same surface, it was possible to photo-emit an electron beam at gradients up to 150MV/m. The test setup and the experimental results are presented

  17. Paired-pulse facilitation achieved in protonic/electronic hybrid indium gallium zinc oxide synaptic transistors

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Li Qiang, E-mail: guoliqiang@ujs.edu.cn; Ding, Jian Ning; Huang, Yu Kai [Micro/Nano Science & Technology Center, Jiangsu University, Zhenjiang, 212013 (China); Zhu, Li Qiang, E-mail: lqzhu@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2015-08-15

    Neuromorphic devices with paired pulse facilitation emulating that of biological synapses are the key to develop artificial neural networks. Here, phosphorus-doped nanogranular SiO{sub 2} electrolyte is used as gate dielectric for protonic/electronic hybrid indium gallium zinc oxide (IGZO) synaptic transistor. In such synaptic transistors, protons within the SiO{sub 2} electrolyte are deemed as neurotransmitters of biological synapses. Paired-pulse facilitation (PPF) behaviors for the analogous information were mimicked. The temperature dependent PPF behaviors were also investigated systematically. The results indicate that the protonic/electronic hybrid IGZO synaptic transistors would be promising candidates for inorganic synapses in artificial neural network applications.

  18. Fast electron transport and heating in ultraintense laser pulse interaction with solid targets

    Science.gov (United States)

    Koenig, Michel; Amiranoff, Francois; Baton, Sophie; Gremillet, Laurent; Martinolli, Emanuele; Batani, Dimitri; Bernardinello, Andrea; Greison, Gabriella; Hall, Tom; Rabec Le Gloahec, Marc; Rousseaux, Christophe; Santos, Joao

    2000-10-01

    In the context of the fast electron transport in solid matter and the fast ignitor scheme, we report on results from ultraintense laser pulse interaction with thick targets. Experiments have been performed at LULI with the 100 TW CPA Nd:glass laser, at intensities up to a few 10^19 W/cm^2. Images obtained from classical and chirped-pulse time-resolved reflectometry diagnostics of the back-side target give evidence of the rear surface heating; the geometry and the dynamics of the energy deposition of the relativistic electrons flux into matter are also inferred.

  19. Paired-pulse facilitation achieved in protonic/electronic hybrid indium gallium zinc oxide synaptic transistors

    International Nuclear Information System (INIS)

    Neuromorphic devices with paired pulse facilitation emulating that of biological synapses are the key to develop artificial neural networks. Here, phosphorus-doped nanogranular SiO2 electrolyte is used as gate dielectric for protonic/electronic hybrid indium gallium zinc oxide (IGZO) synaptic transistor. In such synaptic transistors, protons within the SiO2 electrolyte are deemed as neurotransmitters of biological synapses. Paired-pulse facilitation (PPF) behaviors for the analogous information were mimicked. The temperature dependent PPF behaviors were also investigated systematically. The results indicate that the protonic/electronic hybrid IGZO synaptic transistors would be promising candidates for inorganic synapses in artificial neural network applications

  20. Paired-pulse facilitation achieved in protonic/electronic hybrid indium gallium zinc oxide synaptic transistors

    Directory of Open Access Journals (Sweden)

    Li Qiang Guo

    2015-08-01

    Full Text Available Neuromorphic devices with paired pulse facilitation emulating that of biological synapses are the key to develop artificial neural networks. Here, phosphorus-doped nanogranular SiO2 electrolyte is used as gate dielectric for protonic/electronic hybrid indium gallium zinc oxide (IGZO synaptic transistor. In such synaptic transistors, protons within the SiO2 electrolyte are deemed as neurotransmitters of biological synapses. Paired-pulse facilitation (PPF behaviors for the analogous information were mimicked. The temperature dependent PPF behaviors were also investigated systematically. The results indicate that the protonic/electronic hybrid IGZO synaptic transistors would be promising candidates for inorganic synapses in artificial neural network applications.

  1. Flexible attosecond beamline for high harmonic spectroscopy and XUV/near-IR pump probe experiments requiring long acquisition times

    Energy Technology Data Exchange (ETDEWEB)

    Weber, S. J., E-mail: sebastien.weber@cea.fr; Manschwetus, B.; Billon, M.; Bougeard, M.; Breger, P.; Géléoc, M.; Gruson, V.; Lin, N.; Ruchon, T.; Salières, P.; Carré, B. [Commissariat l’Energie Atomique, Laser, Interactions and Dynamics Laboratory (LIDyL), DSM/IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Böttcher, M.; Huetz, A.; Picard, Y. J. [ISMO, UMR 8214, Université Paris-Sud, Batiment 350, Orsay (France)

    2015-03-15

    We describe the versatile features of the attosecond beamline recently installed at CEA-Saclay on the PLFA kHz laser. It combines a fine and very complete set of diagnostics enabling high harmonic spectroscopy (HHS) through the advanced characterization of the amplitude, phase, and polarization of the harmonic emission. It also allows a variety of photo-ionization experiments using magnetic bottle and COLTRIMS (COLd Target Recoil Ion Momentum Microscopy) electron spectrometers that may be used simultaneously, thanks to a two-foci configuration. Using both passive and active stabilization, special care was paid to the long term stability of the system to allow, using both experimental approaches, time resolved studies with attosecond precision, typically over several hours of acquisition times. As an illustration, applications to multi-orbital HHS and electron-ion coincidence time resolved spectroscopy are presented.

  2. Optical control of electron trapping: Generation of comb-like electron beams for tunable, pulsed, multi-color radiation sources

    Science.gov (United States)

    Kalmykov, Serge

    2014-10-01

    All-optical control over the electron phase space in laser-plasma accelerators enables production of ``designer'' electron beams that can be optimized for specific applications. GeV-scale acceleration with sub-100 TW (rather than PW) laser pulses, at repetition rates orders-of-magnitude higher than permitted by existing PW facilities, in a few-mm (rather than cm) length plasmas, requires maintaining an accelerating gradient as high as 10 GV/cm. This, in turn, dictates acceleration in the blowout regime in a dense plasma (~1019 cm-3). These highly dispersive plasmas rapidly transform the drive pulse into a relativistic optical shock, causing the plasma wake bucket (electron density bubble) to constantly expand, trapping background electrons, greatly degrading beam quality. We show that these effects can be overcome using a high-bandwidth driver (over 1/2 the carrier frequency) with a negative frequency chirp. Temporally advancing higher frequencies (thus compensating for the plasma-induced nonlinear frequency red-shift) and propagating the pulse in a plasma channel (to suppress diffraction of its leading edge) delays pulse self-steepening through electron dephasing and extends the dephasing length. As a result, continuous injection is suppressed and electron energy is boosted to the GeV level. In addition, periodic self-injection in the channel produces a sequence of femtosecond-length, quasi-monoenergetic bunches. The number of these spectral components, their charge, energy, and energy separation can be controlled by varying the channel radius and length, whereas accumulation of the noise (viz. continuously injected charge) is prevented by the negative chirp of the driver. This level of control is hard to achieve with conventional accelerator techniques. It is demonstrated that these clean, polychromatic, comb-like beams can drive high-brightness, tunable, multi-color gamma-ray sources. Work is supported by the US DOE Grant DE-SC0008382 and NSF Grant PHY-1104683.

  3. Pulse radiolytic studies of electron transfer processes and applications to solar photochemistry. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Neta, P.

    1995-02-01

    The pulse radiolysis technique is applied to the study of electron transfer processes in a variety of chemical systems. Reactive intermediates are produced in solution by electron pulse irradiation and the kinetics of their reactions are followed by time resolved absorption spectrophotometry. Complementary experiments are carried out with excimer laser flash photolysis. These studies are concerned with mechanisms, kinetics, and thermodynamics of reactions of organic and inorganic radicals and unstable oxidation states of metal ions. Reactions are studied in both aqueous and non-aqueous solutions. The studies focus on the unique ability of pulse radiolysis to provide absolute rate constants for reactions of many inorganic radicals and organic peroxyl radicals, species that are key intermediates in many chemical processes. A special concern of this work is the study of electron transfer reactions of metalloporphyrins, which permits evaluation of these molecules as intermediates in solar energy conversion. Metalloporphyrins react with free radicals via electron transfer, involving the ligand or the metal center, or via bonding to the metal, leading to a variety of chemical species whose behavior is also investigated. The highlights of the results during the past three years are summarized below under the following sections: (a) electron transfer reactions of peroxyl radicals, concentrating on the characterization of new peroxyl radicals derived from vinyl, phenyl, other aryl, and pyridyl; (b) solvent effects on electron transfer reactions of inorganic and organic peroxyl radicals, including reactions with porphyrins, and (c) electron transfer and alkylation reactions of metalloporphyrins and other complexes.

  4. Electron transport measurements in methane using an improved pulsed Townsend technique

    International Nuclear Information System (INIS)

    An improved pulsed Townsend technique for the measurement of electron transport parameters in gases is described. The accuracy and sensitivity of the technique have been investigated by performing, respectively, electron attachment coefficient measurements in pure O2 over a wide range of E/N at selected O2 pressures and by determining the electron attachment and ionization coefficients and electron drift velocity in CH4 over a wide E/N range. Good agreement has been obtained between the present and the previously published electron attachment coefficients in O2 and for the drift velocity measurements in CH4. The data on the electron attachment coefficient in CH4 (measured for the first time) showed that with the present improved pulsed Townsend method, electron attachment coefficients up to 10 times smaller than the ionization coefficients at a given E/N value can be accurately measured. Our measurements of the electron attachment and ionization coefficients in CH4 are in good agreement with a Boltzmann equation analysis of the electron gain and loss processes in CH4 using published electron scattering cross sections for this molecule

  5. Electron-Beam Switches For A High Peak Power Sled-II Pulse Compressor

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay, L. [Yale Univ., New Haven, CT (United States)

    2015-12-02

    Omega-P demonstrated triggered electron-beam switches on the L=2 m dual-delay-line X-band pulse compressor at Naval Research Laboratory (NRL). In those experiments, with input pulses of up to 9 MW from the Omega-P/NRL X-band magnicon, output pulses having peak powers of 140-165 MW and durations of 16-20 ns were produced, with record peak power gains M of 18-20. Switch designs are described based on the successful results that should be suitable for use with the existing SLAC SLED-II delay line system, to demonstrate C=9, M=7, and n>>78%, yielding 173ns compressed pulses with peak powers up to 350MW with input of a single 50-MW.

  6. Femtosecond laser microchannels fabrication based on electrons dynamics control using temporally or spatially shaped pulses

    Science.gov (United States)

    Yan, Xueliang; Hu, Jie; Li, Xiaowei; Xia, Bo; Liu, Pengjun; Lu, Yongfeng; Jiang, Lan

    2014-11-01

    With ultrashort pulse durations and ultrahigh power densities, femtosecond laser presents unique advantages of high precision and high quality fabrication of microchannels in transparent materials. In our study, by shaping femtosecond laser pulse energy distribution in temporal or spatial domains, localized transient electrons dynamics and the subsequent processes, such as phase changes, can be controlled, leading to the dramatic increases in the capability of femtosecond laser microchannels fabrication. The temporally shaped femtosecond laser pulse trains can significantly enhance the material removal rate in both water-assisted femtosecond laser drilling and femtosecond laser irradiation followed by chemical etching. Besides, high-aspect-ratio and small-diameter microchannels are drilled by spatially shaped femtosecond laser pulses.

  7. A spectrometer for pulsed and continuous electron and photon radiation

    International Nuclear Information System (INIS)

    A few-channel spectrometer for the determination of absolute fluence and energy distributions (spectra) of electrons and photons was developed. It consists of thermoluminescence detectors (TLDs) placed in a stack of different absorbers. From the measured depth dose curve the impinging particle spectra can be derived via deconvolution methods (data evaluation). In mixed radiation fields it is necessary to take into account information in addition to the measured depth dose curve (additional pre-information) for the data evaluation. In addition, a nuclear track detector (CR-39) is implemented in the spectrometer to detect ions and protons. The spectrometer was successfully applied in different areas. (author)

  8. Characterization of relativistic electrons generated by a cone guiding laser pulse

    Institute of Scientific and Technical Information of China (English)

    Liu Hong-Jie; Qian Feng; Cao Lei-Feng; Zhang Bao-Han; Zheng Zhi-Jian; Gu Yu-Qiu; Zhou Wei-Min; Yu Jin-Qing; Zhu Bin; Wu Yu-Chi; Shan Lian-Qiang; Wen Xian-Lun; Li Fang

    2012-01-01

    We demonstrated the interaction of a gold cone target with a femto second(fs)laser pulse above the relativistic intensity of 1.37×1018 μm2W/cm2.Relativistic electrons with energy above 2 MeV were observed.A 25%-40% increase of the electron temperature is achieved compared to the case when a plane gold target is used.The electron temperature increase results from the guiding of the laser beam at the tip and the intense quasistatic magnetic field in the cone geometry.The behavior of the relativistic electrons is verified in our 2D-PIC simulations.

  9. Attosecond x-ray source generation from two-color polarized gating plasmonic field enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Liqiang [College of Science, Liaoning University of Technology, Jinzhou 121000 (China); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Yuan, Minghu [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Chu, Tianshu [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)

    2013-12-15

    The plasmonic field enhancement from the vicinity of metallic nanostructures as well as the polarization gating technique has been utilized to the generation of the high order harmonic and the single attosecond x-ray source. Through numerical solution of the time-dependent Schrödinger equation, for moderate the inhomogeneity and the polarized angle of the two fields, we find that not only the harmonic plateau has been extended and enhanced but also the single short quantum path has been selected to contribute to the harmonic. As a result, a series of 50 as pulses around the extreme ultraviolet and the x-ray regions have been obtained. Furthermore, by investigating the other parameters effects on the harmonic emission, we find that this two-color polarized gating plasmonic field enhancement scheme can also be achieved by the multi-cycle pulses, which is much better for experimental realization.

  10. VLF wave emissions by pulsed and dc electron beams in space. I - Spacelab 2 observations

    Science.gov (United States)

    Reeves, G. D.; Banks, P. M.; Neubert, T.; Bush, R. I.; Williamson, P. R.

    1988-01-01

    The properties of radio waves generated by electron beams in space were investigated using data from the wideband wave receiver on the Spacelab 2. The VLF observations were found to confirm the results of the STS 3/OSS-1 mission. It was found that a 1-keV electron beam injected from the orbiter produced copious broadband electromagnetic emissions. When the electron beam was square-wave modulated, narrow-band emissions at the pulsing frequency and harmonics of that frequency were produced along with the broadband emissions. The observations indicated that dc 50-mA electron beams and pulsed 50-percent duty-cycle 100-mA beams produce broadband radiation which is comparable in intensity and spectral shape at all points for which the wave field was sampled.

  11. Pulsed electron beam precharger. Technical progress report No. 1, September 1, 1989--November 30, 1989

    Energy Technology Data Exchange (ETDEWEB)

    Finney, W.C. [ed.; Shelton, W.N.

    1989-12-31

    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.

  12. Electron-beam pulse annealed Ti-implanted GaP

    Science.gov (United States)

    Werner, Z.; Barlak, M.; Ratajczak, R.; Konarski, P.; Markov, A. M.; Heller, R.

    2016-08-01

    Gallium phosphide heavily doped with substitutional titanium is a prospective material for intermediate band solar cells. To manufacture such a material, single crystals of GaP were implanted with 120 keV Ti ions to doses between 5 × 1014 cm-2 and 5 × 1015 cm-2. They were next pulse annealed with 2 μs electron-beam pulses of electron energy of about 13 keV and pulse energy density between 1 and 2 Jcm-2. The samples were studied by channeled Rutherford Backscattering, particle induced X-ray emission, and SIMS. The results show full recovery of crystal structure damaged by implantation and good retention of the implanted titanium without, however, its significant substitution at crystal sites.

  13. Pulse propagation in storage ring free electron laser devices and longitudinal instabilities

    CERN Document Server

    Bartolini, R; Giannessi, L; Mezi, L

    2002-01-01

    We develop a self-consistent general purpose code modelling the storage ring free electron laser devices. The code accounts for the beam longitudinal dynamics and the laser pulse propagation and is capable of reproducing the wealth of phenomenology associated with the laser-electron beam interplay and provides a deeper understanding of the mechanisms underlying the role of the laser in the suppression of instabilities of longitudinal type.

  14. Generation of VUV ultra-short coherent optical pulses using electron storage rings

    OpenAIRE

    Curbis, Francesca

    2008-01-01

    The need of coherent and intense pulsed radiation is spread among many research disciplines, such as biology, nanotechnology, physics, chemistry and medicine. The synchrotron light from traditional sources only partially meets these characteristics. A new kind of light source has been conceived and developed in the last decades: the Free-Electron Laser (FEL). The FEL process relies on the interaction between a relativistic electron beam and an electromagnetic wave in presence of a...

  15. Pulse propagation in storage ring free electron laser devices and longitudinal instabilities

    International Nuclear Information System (INIS)

    We develop a self-consistent general purpose code modelling the storage ring free electron laser devices. The code accounts for the beam longitudinal dynamics and the laser pulse propagation and is capable of reproducing the wealth of phenomenology associated with the laser-electron beam interplay and provides a deeper understanding of the mechanisms underlying the role of the laser in the suppression of instabilities of longitudinal type

  16. Formation control of electron-hole droplets in diamond by a weak pulse injection

    Energy Technology Data Exchange (ETDEWEB)

    Omachi, J; Yoshioka, K; Kuwata-Gonokami, M [Department of Applied Physics, Graduate School of Engineering, University of Tokyo and CREST-JST, Tokyo 113-8656 (Japan); Naka, N, E-mail: gonokami@ap.t.u-tokyo.ac.j [Department of Physics, Kyoto University and PRESTO, JST, Kyoto 606-8502 (Japan)

    2009-02-01

    We demonstrate a formation control of electron-hole droplets (EHD) in diamond by a weak pulse injection. At high temperatures, we find a large enhancement of the luminescence signal from EHD. On the other hand, the enhancement decreases when we lower the temperature, indicating a decrease in the droplet size and the instability of EHD. In this region, electron-hole ensembles might form a new phase consisting of multi-excitonic clusters.

  17. Desorption of H atoms from graphite (0001) using XUV free electron laser pulses

    DEFF Research Database (Denmark)

    Siemer, B.; Olsen, Thomas; Hoger, T.;

    2010-01-01

    The desorption of neutral H atoms from graphite with femtosecond XUV pulses is reported. The velocity distribution of the atoms peaks at extremely low kinetic energies. A DFT-based electron scattering calculation traces this distribution to desorption out of specific adsorption sites on graphite...

  18. Intense giga watt pulsed electron accelerators for HPM and FXR generation

    International Nuclear Information System (INIS)

    New development in the field of high power pulsed accelerator is the KALI-30GW system capable of delivering 1 MV, 30 kA, 80 ns electron beam pulses. This system has all indigenous components including energy storage capacitors and transformer oil as the dielectric and insulating medium. The energy balance in each stage of sub-system has been maintained to have better efficiency of energy transfer and improving the life of associated insulators. It has been used for high power microwaves generation using reflex triode and relativistic magnetron successfully. A suitable flash-X-rays gun is also designed and developed for this system. The results of these experiments will be presented in this paper. In order to make pulsed electron accelerators compact and repetitive, two more systems are developed in Accelerator and Pulse Power Division, BTDG, BARC which are Linear Induction Accelerator (LIA-400) tested up to 400 kV, 4 kA,100 ns,1-300 Hz and repetitive Marx generator rated for 300 kV, 12 kA, 300 ns, 10 Hz are also developed which are being used for Intentional ElectroMagnetic Interference (IEMI) studies of various electronics circuitry/devices. A few experimental investigations are also done using these systems to understand the effect of cathode material, relativistic electron beam and flash-X-rays emission. Latest results are being illustrated. (author)

  19. Electron dynamics and prompt ablation of aluminum surface excited by intense femtosecond laser pulse

    Science.gov (United States)

    Ionin, A. A.; Kudryashov, S. I.; Makarov, S. V.; Seleznev, L. V.; Sinitsyn, D. V.

    2014-12-01

    Thin aluminum film homogeneously heated by intense IR femtosecond laser pulses exhibits on the excitation timescale consequent fluence-dependent rise and drop of the IR-pump self-reflectivity, followed by its final saturation at higher fluences F > 0.3 J/cm2. This prompt optical dynamics correlates with the initial monotonic increase in the accompanying laser-induced electron emission, which is succeeded by its non-linear (three-photon) increase for F > 0.3 J/cm2. The underlying electronic dynamics is related to the initial saturation of IR resonant interband transitions in this material, followed by its strong instantaneous electronic heating via intraband transitions during the pump pulse resulting in thermionic emission. Above the threshold fluence of 0.3 J/cm2, the surface electronic heating is balanced during the pump pulse by simultaneous cooling via intense plasma removal (prompt ablation). The relationship between the deposited volume energy density in the film and its prompt electronic temperature derived from the self-reflection measurements using a Drude model, demonstrates a kind of electron "liquid-vapor" phase transition, driven by strong cubic optical non-linearity of the photo-excited aluminum.

  20. Lowering effect of radioactive irradiation on breakdown voltage and electron avalanche pulse characteristics

    International Nuclear Information System (INIS)

    In the time resolving measurement of the growing process and breakdown of electron avalanche in a gap of uniform electric field, the phenomenon that DC breakdown voltage slightly lowered was observed when β ray was irradiated as the initial electron source, as compared with unirradiated condition. Beta source used is 90Sr-90Y of 2 mCi in radiative equilibrium. The experimental results and the examination are described in detail. In brief, the remarkable superposition of succeeding avalanche pulse over the preceeding avalanche pulse waveform was observed under the gap condition in which the breakdown voltage decreased in β-ray irradiation. Thus this superposition of avalanche pulses is considered as one of the causes of the breakdown voltage reduction. When β source is used as the initial electron source, the number of supplied initial electrons is very large as compared with unity, and at the same time, a great number of initial electrons can be supplied within the diffusion radius r of avalanche. Then the effect of initial electron number n0 was considered by employing a diagram for breakdown scheme. The transition from Townsend type breakdown to streamer type breakdown occurs owing to increasing n0, and in that condition, the breakdown voltage lowers slightly. (Wakatsuki, Y)

  1. Electromagnetic cascade in high-energy electron, positron, and photon interactions with intense laser pulses

    Science.gov (United States)

    Bulanov, S. S.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

    2013-06-01

    The interaction of high-energy electrons, positrons, and photons with intense laser pulses is studied in head-on collision geometry. It is shown that electrons and/or positrons undergo a cascade-type process involving multiple emissions of photons. These photons can consequently convert into electron-positron pairs. As a result charged particles quickly lose their energy developing an exponentially decaying energy distribution, which suppresses the emission of high-energy photons, thus reducing the number of electron-positron pairs being generated. Therefore, this type of interaction suppresses the development of the electromagnetic avalanche-type discharge, i.e., the exponential growth of the number of electrons, positrons, and photons does not occur in the course of interaction. The suppression will occur when three-dimensional effects can be neglected in the transverse particle orbits, i.e., for sufficiently broad laser pulses with intensities that are not too extreme. The final distributions of electrons, positrons, and photons are calculated for the case of a high-energy e-beam interacting with a counterstreaming, short intense laser pulse. The energy loss of the e-beam, which requires a self-consistent quantum description, plays an important role in this process, as well as provides a clear experimental observable for the transition from the classical to quantum regime of interaction.

  2. System aspects of the ILC-electronics and power pulsing

    CERN Document Server

    Götlicher, P

    2007-01-01

    The requirements for the electronics of an experiment at the international linear collider (ILC) are driven by the bunch structure of the accelerator - short trains (1ms) with bunch to bunch lag of 0.3μs interrupted by long empty intervals (199ms) - and the precision physics. Based on developments of the CALICEcollaboration a system for high granular dense calorimetry is presented. The talk covers the system aspect: — of compact sensors as Si-diodes and multi-pixel Geiger mode photo sensors, — of the electromechanics with components embedded into the PCB’s, — of integrating the functionality needed nearby the sensor into low power ASIC’s, — of a DAQ-chain, in which each channel triggers on its own and the data selection is installed into PC’s and — of calibrating the calorimeter. With the high number of 100 million channels the power consumption and cooling have to be investigated carefully. Calculations demonstrate, that active cooling inside the calorimeters can be avoided. But essential fo...

  3. Carrier-envelope phase effects on the strong-field photoemission of electrons from metallic nanostructures

    CERN Document Server

    Piglosiewicz, Bjoern; Park, Doo Jae; Vogelsang, Jan; Gross, Petra; Manzoni, Cristian; Cerullo, Giulio; Lienau, Christoph

    2013-01-01

    Sharp metallic nanotapers irradiated with few-cycle laser pulses are emerging as a source of highly confined coherent electron wavepackets with attosecond duration and strong directivity. The possibility to steer, control or switch such electron wavepackets by light is expected to pave the way towards direct visualization of nanoplasmonic field dynamics and real-time probing of electron motion in solid state nanostructures. Such pulses can be generated by strong-field induced tunneling and acceleration of electrons in the near-field of sharp gold tapers within one half-cycle of the driving laser field. Here, we show the effect of the carrier-envelope phase of the laser field on the generation and motion of strong-field emitted electrons from such tips. This is a step forward towards controlling the coherent electron motion in and around metallic nanostructures on ultrashort length and time scales.

  4. Transverse electron momentum distribution in tunneling and over the barrier ionization by laser pulses with varying ellipticity

    OpenAIRE

    Ivanov, I. A.; A. S. Kheifets; Calvert, J. E.; Goodall, S.; Wang, X.; Han Xu; Palmer, A. J.; Kielpinski, D.; Litvinyuk, I.V.; Sang, R. T.

    2016-01-01

    We study transverse electron momentum distribution in strong field atomic ionization driven by laser pulses with varying ellipticity. We show, both experimentally and theoretically, that the transverse electron momentum distribution in the tunneling and over the barrier ionization regimes evolves in a qualitatively different way when the ellipticity parameter describing polarization state of the driving laser pulse increases.

  5. Characterization of electrons and x-rays produced using chirped laser pulses in a laser wakefield accelerator

    Science.gov (United States)

    Zhao, T. Z.; Behm, K.; He, Z.-H.; Maksimchuk, A.; Nees, J. A.; Yanovsky, V.; Thomas, A. G. R.; Krushelnick, K.

    2016-11-01

    The electron injection process into a plasma-based laser wakefield accelerator can be influenced by modifying the parameters of the driver pulse. We present an experimental study on the combined effect of the laser pulse duration, pulse shape, and frequency chirp on the electron injection and acceleration process and the associated radiation emission for two different gas types—a 97.5% He and 2.5% N2 mixture and pure He. In general, the shortest pulse duration with minimal frequency chirp produced the highest energy electrons and the most charge. Pulses on the positive chirp side sustained electron injection and produced higher charge, but lower peak energy electrons, compared with negatively chirped pulses. A similar trend was observed for the radiant energy. The relationship between the radiant energy and the electron charge remained linear over a threefold change in the electron density and was independent of the drive pulse characteristics. X-ray spectra showed that ionization injection of electrons into the wakefield generally produced more photons than self-injection for all pulse durations/frequency chirp and had less of a spread in the number of photons around the peak x-ray energy.

  6. James Webb Space Telescope Mid Infra-Red Instrument Pulse-Tube Cryocooler Electronics

    Science.gov (United States)

    Harvey, D.; Flowers, T.; Liu, N.; Moore, K.; Tran, D.; Valenzuela, P.; Franklin, B.; Michaels, D.

    2013-01-01

    The latest generation of long life, space pulse-tube cryocoolers require electronics capable of controlling self-induced vibration down to a fraction of a newton and coldhead temperature with high accuracy down to a few kelvin. Other functions include engineering diagnostics, heater and valve control, telemetry and safety protection of the cryocooler subsystem against extreme environments and operational anomalies. The electronics are designed to survive the thermal, vibration, shock and radiation environment of launch and orbit, while providing a design life in excess of 10 years on-orbit. A number of our current generation high reliability radiation-hardened electronics units are in various stages of integration on several space flight payloads. This paper describes the features and performance of our latest flight electronics designed for the pulse-tube cryocooler that is the pre-cooler for a closed cycle Joule-Thomson cooler providing 6K cooling for the James Webb Space Telescope (JWST) Mid Infra-Red Instrument (MIRI). The electronics is capable of highly accurate temperature control over the temperature range from 4K to 15K. Self-induced vibration is controlled to low levels on all harmonics up to the 16th. A unique active power filter controls peak-to-peak reflected ripple current on the primary power bus to a very low level. The 9 kg unit is capable of delivering 360W continuous power to NGAS's 3-stage pulse-tube High-Capacity Cryocooler (HCC).

  7. Electron self-injection during interaction of tightly focused few-cycle laser pulses with underdense plasma

    Science.gov (United States)

    Zhidkov, Alexei; Fujii, Takashi; Nemoto, Koshichi

    2008-09-01

    We study the interaction of short laser pulses tightly focused in a tiny volume proportional to the cube of the pulse wavelength (λ3) with underdense plasma by means of real-geometry particle-in-cell simulations. Underdense plasma irradiated by relatively low-energy λ3 (and λ2 ) laser pulses is shown to be an efficient source of multi-MeV electrons, ˜50nC/J , and coherent hard x rays, despite a strong pulse diffraction. Transverse wave breaking in the vicinity of the laser focus is found to give rise to an immense electron charge loading to the acceleration phase of a laser wake field. A strong blowout regime provoked by the injected electrons resulting in the distribution of accelerated electrons is found for λ3 pulses (further electron acceleration driving by λ2 pulses runs in the usual way). With an increase of pulse energy, wiggling and electron-hose instabilities in the λ3 pulse wake are recognized in the blowout regime. For higher-energy λ3 pulses, the injected beams are well modulated and may serve as a good source of coherent x rays.

  8. Microsecond resolved electron density measurements with a hairpin resonator probe in a pulsed ICP discharge

    CERN Document Server

    Peterson, David; Larson, Lynda; Shannon, Steven

    2016-01-01

    Time resolved electron density measurements in pulsed RF discharges are shown using a hairpin resonance probe using low cost electronics, on par with normal Langmuir probe boxcar mode operation. Time resolution of less than one microsecond has been demonstrated. A signal generator produces the applied microwave frequency; the reflected waveform is passed through a directional coupler and filtered to remove the RF component. The signal is heterodyned with a frequency mixer and read by an oscilloscope. At certain points during the pulse, the plasma density is such that the applied frequency is the same as the resonance frequency of the probe/plasma system, creating a dip in the reflected signal. The applied microwave frequency is shifted in small increments in a frequency boxcar routine to determine the density as a function of time. The system uses a grounded probe to produce low cost, high fidelity, and highly reproducible electron density measurements that can work in harsh chemical environments. Measurement...

  9. Generation of Intense Narrow-Band Tunable Terahertz Radiation from Highly Bunched Electron Pulse Train

    Science.gov (United States)

    Li, Heting; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

    2016-07-01

    We present the analysis and start-to-end simulation of an intense narrow-band terahertz (THz) source with a broad tuning range of radiation frequency, using a single-pass free electron laser (FEL) driven by a THz-pulse-train photoinjector. The fundamental radiation frequency, corresponding to the spacing between the electron microbunches, can be easily tuned by varying the spacing time between the laser micropulses. Since the prebunched electron beam is highly bunched at the first several harmonics, with the harmonic generation technique, the radiation frequency range can be further enlarged by several times. The start-to-end simulation results show that this FEL is capable of generating a few tens megawatts power, several tens micro-joules pulse energy, and a few percent bandwidth at the frequencies of 0.5-5 THz. In addition, several practical issues are considered.

  10. Mechanism of pulsed electron irradiation of the PLZT X/65/35 ceramics

    International Nuclear Information System (INIS)

    The comprehensive study of high-current pulsed electron irradiation effect on the structure and lattice dynamics as well as Atomic Force (AFM) and Laser Confocal Scanning microscope (LSCM) surface imaginaries of PLZT 8/65/35 ceramics have been performed. X-ray powder diffraction studies show the transformation of the cubic perovskite Pm-3m (Z=1) into orthorhombic Pmmm (Z=1) structure for the sample irradiated by one pulse (dose 6 x 1014electrons/cm 2) and into cubic Pm-3m with increased lattice volume and more ordered structure at irradiating by 10 and 100 pulses (dose 6 x 10 15 and 6 x 1016el/cm 2). A consequence, the changes of number, intensity and phonon modes position occur in Raman spectroscopy data. It should be noted that the annealing at 200 C of the single irradiated sample leads to the partly restoration of the orthorhombic structure. AFM and LSCM surface imaginaries correlate well with X-ray diffraction and Raman measurements. The possible mechanism of pulsed electron irradiation effect in PLZT 8/65/35 ceramics is discussed. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. George E. Pake Prize Lecture: Pulsed Laser Deposition and the Oxide Electronics Revolution

    Science.gov (United States)

    Venkatesan, T.

    2012-02-01

    The discovery of the Pulsed Laser Deposition (PLD) Process at Bellcore was followed by a stream of advances in the epitaxial growth of oxides and a variety of heterostructures and interfaces. Today Oxide Electronics is a fascinating field with a great deal of new Science and potential for applications. Following a discussion of these events, my talk will focus on the adventure involved in creating a new company, Neocera, and, at the same time, pushing ahead in the evolving field of oxide electronics. There, electron spin, pairing, and alignment to create superconductivity and magnetism have opened up new frontiers for research and materials development.

  12. Dissociative multiple ionization of diatomic molecules by extreme-ultraviolet free-electron-laser pulses

    DEFF Research Database (Denmark)

    Madsen, Lars Bojer; Leth, Henriette Astrup

    2011-01-01

    Nuclear dynamics in dissociative multiple ionization processes of diatomic molecules exposed to extreme-ultraviolet free-electron-laser pulses is studied theoretically using the Monte Carlo wave packet approach. By simulated detection of the emitted electrons, the model reduces a full propagation...... of the system to propagations of the nuclear wave packet in one specific electronic charge state at a time. Suggested ionization channels can be examined, and kinetic energy release spectra for the nuclei can be calculated and compared with experiments. Double ionization of O2 is studied as an...

  13. Lateral resolution in focused electron beam-induced deposition: scaling laws for pulsed and static exposure

    Energy Technology Data Exchange (ETDEWEB)

    Szkudlarek, Aleksandra [Empa, Laboratory for Mechanics of Materials and Nanostructures, Thun (Switzerland); AGH University of Science and Technology, Department of Solid State Physics, Faculty of Physics and Applied Computer Science, Krakow (Poland); Szmyt, Wojciech; Kapusta, Czeslaw [AGH University of Science and Technology, Department of Solid State Physics, Faculty of Physics and Applied Computer Science, Krakow (Poland); Utke, Ivo [Empa, Laboratory for Mechanics of Materials and Nanostructures, Thun (Switzerland)

    2014-12-15

    In this work, we review the single-adsorbate time-dependent continuum model for focused electron beam-induced deposition (FEBID). The differential equation for the adsorption rate will be expressed by dimensionless parameters describing the contributions of adsorption, desorption, dissociation, and the surface diffusion of the precursor adsorbates. The contributions are individually presented in order to elucidate their influence during variations in the electron beam exposure time. The findings are condensed into three new scaling laws for pulsed exposure FEBID (or FEB-induced etching) relating the lateral resolution of deposits or etch pits to surface diffusion and electron beam exposure dwell time for a given adsorbate depletion state. (orig.)

  14. Laser triggered injection of electrons in a laser wakefield accelerator with the colliding pulse method

    International Nuclear Information System (INIS)

    An injection scheme for a laser wakefield accelerator that employs a counter propagating laser (colliding with the drive laser pulse, used to generate a plasma wake) is discussed. The threshold laser intensity for electron injection into the wakefield was analyzed using a heuristic model based on phase-space island overlap. Analysis shows that the injection can be performed using modest counter propagating laser intensity a1 0 = 1.0. Preliminary experiments were preformed using a drive beam and colliding beam. Charge enhancement by the colliding pulse was observed. Increasing the signal-to-noise ratio by means of a preformed plasma channel is discussed

  15. Low-cost high-speed pulsed amplifiers for electron, ion and photon detectors

    International Nuclear Information System (INIS)

    In this design note, an inexpensive high-speed pulsed amplifier is described for amplification of current pulses derived from single electron or ion detectors (channeltrons, discrete dynode detectors or channel-plates) or single photon detectors (e.g. photomultiplier tubes). The circuit schematic and layout are presented, together with details of the amplifier characteristics. Single particle (e, 2e) coincidence measurements using this new design are compared to results from commercial units. The total cost of the new amplifier is less than 5% of the comparable commercial systems. (technical design note)

  16. Electron acceleration by tightly focused radially polarized few-cycle laser pulses

    Institute of Scientific and Technical Information of China (English)

    Liu Jin-Lu; Sheng Zheng-Ming; Zheng Jun

    2012-01-01

    Within the framework of plane-wave angular spectrum analysis of the electromagnetic field structure,a solution valid for tightly focused radially polarized few-cycle laser pulses propagating in vacuum is presented.The resulting field distribution is significantly different from that based on the paraxial approximation for pulses with either small or large beam diameters.We compare the electron accelerations obtained with the two solutions and find that the energy gain obtained with our new solution is usually much larger than that with the paraxial approximation solution.

  17. Storage ring free electron laser, pulse propagation effects and microwave type instabilities

    International Nuclear Information System (INIS)

    It has been developed a dynamical model accounting for the storage Ring Free Electron Laser evolution including pulse propagation effects and e-beam instabilities of microwave type. It has been analyzed the general conditions under which the on set of the laser may switch off the instability and focus everybody attention on the interplay between cavity mismatch, laser pulsed behavior and e-beam instability dynamics. Particular attention is also devoted to the laser operation in near threshold conditions, namely at an intracavity level just enough to counteract the instability, that show in this region new and interesting effects arises

  18. Spatial and temporal coherence properties of single free-electron laser pulses

    OpenAIRE

    Singer, A; Sorgenfrei, F.; Mancuso, Adrian Paul; Gerasimova, N.; Yefanov, O. M.; Gulden, J.; Gorniak, T.; Senkbeil, T.; Sakdinawat, A.; Liu, Y.; Attwood, D; Dziarzhytski, S.; Mai, D. D.; Treusch, R.; Weckert, E.

    2012-01-01

    The experimental characterization of the spatial and temporal coherence properties of the free-electron laser in Hamburg (FLASH) at a wavelength of 8.0 nm is presented. Double pinhole diffraction patterns of single femtosecond pulses focused to a size of about 10 microns by 10 microns were measured. A transverse coherence length of 6.2 microns in the horizontal and 8.7 microns in the vertical direction was determined from the most coherent pulses. Using a split and delay unit the coherence ti...

  19. Space charge calculations of elliptical cross-section electron pulses in PARMELA

    CERN Document Server

    Koltenbah, B E C

    1999-01-01

    The Boeing version of the PARMELA code has been modified to compute the space charge effects for electron pulses with highly elliptical transverse cross-sections. A dynamic gridding routine has been added to allow good resolution for pulses as they evolve in time. The results from calculations for the chicane buncher in the 1 kW visible FEL beam line at Boeing indicate that the old circular algorithm of the SCHEFF subroutine overestimates the emittance growth in the bend plane by 30-40%.

  20. Nanofocusing of hard X-ray free electron laser pulses using diamond based Fresnel zone plates

    Science.gov (United States)

    David, C.; Gorelick, S.; Rutishauser, S.; Krzywinski, J.; Vila-Comamala, J.; Guzenko, V. A.; Bunk, O.; Färm, E.; Ritala, M.; Cammarata, M.; Fritz, D. M.; Barrett, R.; Samoylova, L.; Grünert, J.; Sinn, H.

    2011-08-01

    A growing number of X-ray sources based on the free-electron laser (XFEL) principle are presently under construction or have recently started operation. The intense, ultrashort pulses of these sources will enable new insights in many different fields of science. A key problem is to provide x-ray optical elements capable of collecting the largest possible fraction of the radiation and to focus into the smallest possible focus. As a key step towards this goal, we demonstrate here the first nanofocusing of hard XFEL pulses. We developed diamond based Fresnel zone plates capable of withstanding the full beam of the world's most powerful x-ray laser. Using an imprint technique, we measured the focal spot size, which was limited to 320 nm FWHM by the spectral band width of the source. A peak power density in the focal spot of 4×1017 W/cm2 was obtained at 70 fs pulse length.

  1. Comparison of pulse sequences for R1-based electron paramagnetic resonance oxygen imaging

    Science.gov (United States)

    Epel, Boris; Halpern, Howard J.

    2015-05-01

    Electron paramagnetic resonance (EPR) spin-lattice relaxation (SLR) oxygen imaging has proven to be an indispensable tool for assessing oxygen partial pressure in live animals. EPR oxygen images show remarkable oxygen accuracy when combined with high precision and spatial resolution. Developing more effective means for obtaining SLR rates is of great practical, biological and medical importance. In this work we compared different pulse EPR imaging protocols and pulse sequences to establish advantages and areas of applicability for each method. Tests were performed using phantoms containing spin probes with oxygen concentrations relevant to in vivo oxymetry. We have found that for small animal size objects the inversion recovery sequence combined with the filtered backprojection reconstruction method delivers the best accuracy and precision. For large animals, in which large radio frequency energy deposition might be critical, free induction decay and three pulse stimulated echo sequences might find better practical usage.

  2. Spatial and temporal coherence properties of single free-electron laser pulses

    CERN Document Server

    Singer, A; Mancuso, A P; Gerasimova, N; Yefanov, O M; Gulden, J; Gorniak, T; Senkbeil, T; Sakdinawat, A; Liu, Y; Attwood, D; Dziarzhytski, S; Mai, D D; Treusch, R; Weckert, E; Salditt, T; Rosenhahn, A; Wurth, W; Vartanyants, I A

    2015-01-01

    The experimental characterization of the spatial and temporal coherence properties of the free-electron laser in Hamburg (FLASH) at a wavelength of 8.0 nm is presented. Double pinhole diffraction patterns of single femtosecond pulses focused to a size of about 10 microns by 10 microns were measured. A transverse coherence length of 6.2 microns in the horizontal and 8.7 microns in the vertical direction was determined from the most coherent pulses. Using a split and delay unit the coherence time of the pulses produced in the same operation conditions of FLASH was measured to be 1.75 fs. From our experiment we estimated the degeneracy parameter of the FLASH beam to be on the order of $10^{10}$ to $10^{11}$, which exceeds the values of this parameter at any other source in the same energy range by many orders of magnitude.

  3. Electron Acceleration and the Propagation of Ultrashort High-Intensity Laser Pulses in Plasmas

    International Nuclear Information System (INIS)

    Reported are interactions of high-intensity laser pulses (λ=810 nm and I≤3x1018 W /cm2 ) with plasmas in a new parameter regime, in which the pulse duration (τ=29 fs ) corresponds to 0.6-2.6 plasma periods. Relativistic filamentation is observed to cause laser-beam breakup and scattering of the beam out of the vacuum propagation angle. A beam of megaelectronvolt electrons with divergence angle as small as 1 degree sign is generated in the forward direction, which is correlated to the growth of the relativistic filamentation. Raman scattering, however, is found to be much less than previous long-pulse results. (c) 2000 The American Physical Society

  4. Experimental evidence of nonthermal acceleration of relativistic electrons by an intensive laser pulse.

    Science.gov (United States)

    Kuramitsu, Y; Nakanii, N; Kondo, K; Sakawa, Y; Mori, Y; Miura, E; Tsuji, K; Kimura, K; Fukumochi, S; Kashihara, M; Tanimoto, T; Nakamura, H; Ishikura, T; Takeda, K; Tampo, M; Kodama, R; Kitagawa, Y; Mima, K; Tanaka, K A; Hoshino, M; Takabe, H

    2011-02-01

    Nonthermal acceleration of relativistic electrons is investigated with an intensive laser pulse. An energy distribution function of energetic particles in the universe or cosmic rays is well represented by a power-law spectrum, therefore, nonthermal acceleration is essential to understand the origin of cosmic rays. A possible candidate for the origin of cosmic rays is wakefield acceleration at relativistic astrophysical perpendicular shocks. The wakefield is considered to be excited by large-amplitude precursor light waves in the upstream of the shocks. Substituting an intensive laser pulse for the large amplitude light waves, we performed a model experiment of the shock environments in a laboratory plasma. An intensive laser pulse was propagated in a plasma tube created by imploding a hollow polystyrene cylinder, as the large amplitude light waves propagated in the upstream plasma at an astrophysical shock. Nonthermal electrons were generated, and the energy distribution functions of the electrons have a power-law component with an index of ~2. We described the detailed procedures to obtain the nonthermal components from data obtained by an electron spectrometer.

  5. Accessing electronic correlations by half-cycle pulses and time-resolved spectroscopy

    CERN Document Server

    Pavlyukh, Y

    2015-01-01

    Ultrashort non-resonant electromagnetic pulses applied to effective one-electron systems may operate on the electronic state as a position or momentum translation operator. As derived here, extension to many-body correlated systems exposes qualitatively new aspects. For instance, to the lowest order in the electric field intensity the action of the pulse is expressible in terms of the two-body reduced density matrix enabling thus to probe various facets of electronic correlations. As an experimental realization we propose a pump-probe scheme in which after a weak, swift "kick" by the non-resonant pulse the survival probability for remaining in the initial state is measured. This probability we correlate to the two-body reduced density matrix. Since the strength of electronic correlation is bond-length sensitive, measuring the survival probability may allow for a direct insight into the bond-dependent two-body correlation in the ground state. As an illustration, full numerical calculations for two molecular sy...

  6. Measurement and laser control of attosecond charge migration in ionized iodoacetylene.

    Science.gov (United States)

    Kraus, P M; Mignolet, B; Baykusheva, D; Rupenyan, A; Horný, L; Penka, E F; Grassi, G; Tolstikhin, O I; Schneider, J; Jensen, F; Madsen, L B; Bandrauk, A D; Remacle, F; Wörner, H J

    2015-11-13

    The ultrafast motion of electrons and holes after light-matter interaction is fundamental to a broad range of chemical and biophysical processes. We advanced high-harmonic spectroscopy to resolve spatially and temporally the migration of an electron hole immediately after ionization of iodoacetylene while simultaneously demonstrating extensive control over the process. A multidimensional approach, based on the measurement and accurate theoretical description of both even and odd harmonic orders, enabled us to reconstruct both quantum amplitudes and phases of the electronic states with a resolution of ~100 attoseconds. We separately reconstructed quasi-field-free and laser-controlled charge migration as a function of the spatial orientation of the molecule and determined the shape of the hole created by ionization. Our technique opens the prospect of laser control over electronic primary processes. PMID:26494175

  7. Electron dynamics of molecular double ionization by circularly polarized laser pulses

    International Nuclear Information System (INIS)

    Using the classical ensemble method, we have investigated double ionization (DI) of diatomic molecules driven by circularly polarized laser pulses with different internuclear distances (R). The results show that the DI mechanism changes from sequential double ionization (SDI) to nonsequential double ionization (NSDI) as the internuclear distance increases. In SDI range, the structure of the electron momentum distribution changes seriously as R increases, which indicates the sensitive dependence of the release times of the two electrons on R. For NSDI, because of the circular polarization, the ionization of the second electron is not through the well-known recollision process but through a process where the first electron ionizes over the inner potential barrier of the molecule, moves directly towards the other nucleus, and kicks out the second electron

  8. Acceleration of electrons under the action of petawatt-class laser pulses onto foam targets

    Science.gov (United States)

    Pugachev, L. P.; Andreev, N. E.; Levashov, P. R.; Rosmej, O. N.

    2016-09-01

    Optimization study for future experiments on interaction of petawatt laser pulses with foam targets was done by 3D PIC simulations. Densities in the range 0.5nc-nc and thicknesses in the range 100 - 500 μm of the targets were considered corresponding to those which are currently available. It is shown that heating of electrons mainly occurs under the action of the ponderomotive force of a laser pulse in which amplitude increases up to three times because of self-focusing effect in underdense plasma. Accelerated electrons gain additional energy directly from the high-frequency laser field at the betatron resonance in the emerging plasma density channels. For thicker targets a higher number of electrons with higher energies are obtained. The narrowing of the angular distribution of electrons for thicker targets is explained by acceleration in multiple narrow filaments. Obtained energies of accelerated electrons can be approximated by Maxwell distribution with the temperature 8.5 MeV. The charge carried by electrons with energies higher than 30 MeV is about 30 nC, that is 3-4 order of magnitude higher than the charge predicted by the ponderomotive scaling for the incident laser amplitude.

  9. Systems of Electronic Overcurrent Protection in Pulse Power Generator Operating on Plasma Load

    Directory of Open Access Journals (Sweden)

    Dmitriy V. Godun

    2013-01-01

    Full Text Available Schematic peculiarities of pulsed power source and modulator-shaper for working on high instability plasma load are discussed. In its construction should be provided for several levels of overcurrent protection. First of all modules of electronic protection should be integrated into the control driver system of IGBT modules and must provide a quick disconnect power switches in excess of the allowable values of pulse current. The next level of overcurrent protection in pulse power generator is a protection against overcurrent in the load circuit. Operating threshold of current protection in this case must be set to the maximum value of current in the secondary circuit. In order to limit the emission of stray voltage on the power pulses in a moment of switching of power switches a restrictive RC snubbers parallel to the collectors and the emitters of transistors must be installed. It is also appropriate application of software-controlled configurating of electrical power at the outputof a pulsed power supply.

  10. Improved wear resistance of Al-15Si alloy with a high current pulsed electron beam treatment

    Science.gov (United States)

    Hao, Y.; Gao, B.; Tu, G. F.; Li, S. W.; Dong, C.; Zhang, Z. G.

    2011-07-01

    A hypereutectic Al-15Si alloy (Si 15 wt.%, Al balance) was irradiated by high current pulsed electron beam (HCPEB). The HCPEB treatment causes ultra-rapid heating, melting and cooling at the top surface layer. As a result, the special "halo" microstructure centering on the primary Si phase is formed on the surface due to interdiffusion of Al and Si elements. The composition of the "halo" microstructure is distributed continuously from the center to the edge of the "halo". Compared to an untreated matrix, the remelted layer underneath the surface presents single contrast because of the compositional homogeneity after HCPEB treatment. The thickness of the remelted layer increases slightly from 4.4 μm (5 pulses) to 5.6 μm (25 pulses). HCPEB treatment broadens and shifts the diffraction peaks of Al and Si. The lattice parameters of Al decreases due to the formation of a supersaturated solid solution of Al in the melted layer. Through analysis of Raman spectra and transmission electron microscopy (TEM), the amorphous Si (a-Si) and nanocrystalline Si are formed in the near-surface region under multiple bombardments of HCPEB. The relative wear resistance of a 15-pulse sample is effectively improved by a factor of 9, which can be attributed to the formation of metastable structures.

  11. Photonic, Electronic and Atomic Collisions

    Science.gov (United States)

    Fainstein, Pablo D.; Lima, Marco Aurelio P.; Miraglia, Jorge E.; Montenegro, Eduardo C.; Rivarola, Roberto D.

    2006-11-01

    Plenary. Electron collisions - past, present and future / J. W. McConkey. Collisions of slow highly charged ions with surfaces / J. Burgdörfer ... [et al.]. Atomic collisions studied with "reaction-microscopes" / R. Moshammer ... [et al.]. Rydberg atoms: a microscale laboratory for studying electron-molecule tnteractions / F. B. Dunning -- Collisions involvintg photons. Quantum control of photochemical reaction dynamics and molecular functions / M. Yamaki ... [et al.]. Manipulating and viewing Rydberg wavepackets / R. R. Jones. Angle-resolved photoelectrons as a probe of strong-field interactions / M. Vrakking. Ultracold Rydberg atoms in a structured environment / I. C. H. Liu and J. M. Rost. Synchrotron-radiation-based recoil ion momentum spectroscopy of laser cooled and trapped cesium atoms / L. H. Coutinho. Reconstruction of attosecond pulse trains / Y. Mairesse ... [et al.]. Selective excitation of metastable atomic states by Femto- and attosecond laser pulses / A. D. Kondorskiy. Accurate calculations of triple differential cross sections for double photoionization of the hygrogen molecule / W. Vanroose ... [et al.]. Double and triple photoionization of Li and Be / J. Colgan, M. S. Pindzola and F. Robicheaux. Few/many body dynamics in strong laser fields / J. Zanghellini and T. Brabec. Rescattering-induced effects in electron-atom scattering in the presence of a circularly polarized laser field / A. V. Flegel ... [et al.]. Multidimensional photoelectron spectroscopy / P. Lablanquie ... [et al.]. Few photon and strongly driven transitions in the XUV and beyond / P. Lambropoulos, L. A. A. Nikolopoulos and S. I. Themelis. Ionization dynamics of atomic clusters in intense laser pulses / U. Saalmann and J. M. Rost. On the second order autocorrelation of an XUV attosecond pulse train / E. P. Benis ... [et al.]. Evidence for rescattering in molecular dissociation / I. D. Williams ... [et al.]. Photoionizing ions using synchrotron radiation / R. Phaneuf. Photo double

  12. Reflection of femtosecond pulses from soft X-ray free-electron laser by periodical multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Ksenzov, D.; Grigorian, S.; Pietsch, U. [Faculty of Physics, University of Siegen (Germany); Hendel, S.; Bienert, F.; Sacher, M.D.; Heinzmann, U. [Faculty of Physics, University of Bielefeld (Germany)

    2009-08-15

    Recent experiments on a soft X-ray free-electron laser (FEL) source (FLASH in Hamburg) have shown that multilayers (MLs) can be used as optical elements for highly intense X-ray irradiation. An effort to find most appropriate MLs has to consider the femtosecond time structure and the particular photon energy of the FEL. In this paper we have analysed the time response of 'low absorbing' MLs (e.g. such as La/B{sub 4}C) as a function of the number of periods. Interaction of a pulse train of Gaussian shaped sub-pulses using a realistic ML grown by electron-beam evaporation technique has been analysed in the soft-X-ray range. The structural parameters of the MLs were obtained by reflectivity measurements at BESSY II and subsequent profile fittings. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  13. Power pulsing scheme for analog and digital electronics of the vertex detectors at CLIC

    CERN Document Server

    Blanchot, Georges

    2015-01-01

    The precision requirements of the vertex detector at CLIC impose strong limitations on the mass of such a detector (< 0.2% of a radiation length, Xo, per layer). To achieve such a low material budget, ultra-thin hybrid pixel detectors are foreseen, while the mass for cooling and services will be reduced by implementing a power pulsing scheme that takes advantage of the low duty cycle of the accelerator. The principal aim is to achieve significant power reduction without compromising the power integrity supplied to the front-end electronics. This report summarises the study of a power pulsing scheme to power the vertex barrel electronics of the future CLIC experiment. Its main goal is to describe in more detail what has been already presented in TWEPP conferences and other presentations. The report can therefore serve as an operator manual for future use and development of the system

  14. Fully Coherent X-ray Pulses from a Regenerative Amplifier Free Electron Laser

    International Nuclear Information System (INIS)

    We propose and analyze a novel regenerative amplifier free electron laser (FEL) to produce fully coherent x-ray pulses. The method makes use of narrow-bandwidth Bragg crystals to form an x-ray feedback loop around a relatively short undulator. Self-amplified spontaneous emission (SASE) from the leading electron bunch in a bunch train is spectrally filtered by the Bragg reflectors and is brought back to the beginning of the undulator to interact repeatedly with subsequent bunches in the bunch train. The FEL interaction with these short bunches not only amplifies the radiation intensity but also broadens its spectrum, allowing for effective transmission of the x-rays outside the crystal bandwidth. The spectral brightness of these x-ray pulses is about two to three orders of magnitude higher than that from a single-pass SASE FEL

  15. Fully Coherent X-Ray Pulses from a Regenerative-Amplifier Free-Electron Laser

    International Nuclear Information System (INIS)

    We propose and analyze a regenerative-amplifier free-electron laser (FEL) to produce fully coherent, hard x-ray pulses. The method makes use of narrow-bandwidth Bragg crystals to form an x-ray feedback loop around a relatively short undulator. Self-amplified spontaneous emission (SASE) from the leading electron bunch in a bunch train is spectrally filtered by the Bragg reflectors and is brought back to the beginning of the undulator to interact repeatedly with subsequent bunches in the bunch train. The FEL interaction with these short bunches regeneratively amplifies the radiation intensity and broadens its spectrum, allowing for effective transmission of the x rays outside the crystal bandwidth. The spectral brightness of these x-ray pulses is about 2 to 3 orders of magnitude higher than that from a single-pass SASE FEL

  16. Longitudinal and transverse cooling of relativistic electron beams in intense laser pulses

    CERN Document Server

    Yoffe, Samuel R; Noble, Adam; Jaroszynski, Dino A

    2015-01-01

    With the emergence in the next few years of a new breed of high power laser facilities, it is becoming increasingly important to understand how interacting with intense laser pulses affects the bulk properties of a relativistic electron beam. A detailed analysis of the radiative cooling of electrons indicates that, classically, equal contributions to the phase space contraction occur in the transverse and longitudinal directions. In the weakly quantum regime, in addition to an overall reduction in beam cooling, this symmetry is broken, leading to significantly less cooling in the longitudinal than the transverse directions. By introducing an efficient new technique for studying the evolution of a particle distribution, we demonstrate the quantum reduction in beam cooling, and find that it depends on the distribution of energy in the laser pulse, rather than just the total energy as in the classical case.

  17. Subwavelength ripples adjustment based on electron dynamics control by using shaped ultrafast laser pulse trains.

    Science.gov (United States)

    Jiang, Lan; Shi, Xuesong; Li, Xin; Yuan, Yanping; Wang, Cong; Lu, Yongfeng

    2012-09-10

    This study reveals that the periods, ablation areas and orientations of periodic surface structures (ripples) in fused silica can be adjusted by using designed femtosecond (fs) laser pulse trains to control transient localized electron dynamics and corresponding material properties. By increasing the pulse delays from 0 to 100 fs, the ripple periods are changed from ~550 nm to ~255 nm and the orientation is rotated by 90°. The nearwavelength/subwavelength ripple periods are close to the fundamental/second-harmonic wavelengths in fused silica respectively. The subsequent subpulse of the train significantly impacts free electron distributions generated by the previous subpulse(s), which might influence the formation mechanism of ripples and the surface morphology.

  18. Determination of relevant parameters for the use of electronic dosemeters in pulsed fields of ionising radiation.

    Science.gov (United States)

    Zutz, H; Hupe, O; Ambrosi, P; Klammer, J

    2012-09-01

    Active electronic dosemeters using counting techniques are used for radioprotection purposes in pulsed radiation fields in X-ray diagnostics or therapy. The disadvantage of the limited maximum measurable dose rate becomes significant in these radiation fields and leads to some negative effects. In this study, a set of relevant parameters for a dosemeter is described, which can be used to decide whether it is applicable in a given radiation field or not. The determination of these relevant parameters-maximum measurable dose rate in the radiation pulse, dead time of the dosemeter, indication per counting event and measurement cycle time-is specified. The results of the first measurements on the determination of these parameters for an electronic personal dosemeter of the type Thermo Fisher Scientific EPD Mk2 are shown.

  19. Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan; Liu Hongxue; Lu Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Gu, Man [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Khokhlov, Mikhail; Wolf, Stuart A. [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Guilford College, Greensboro, North Carolina 27410 (United States)

    2013-01-14

    Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

  20. Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

    Science.gov (United States)

    Comes, Ryan; Gu, Man; Khokhlov, Mikhail; Liu, Hongxue; Lu, Jiwei; Wolf, Stuart A.

    2013-01-01

    Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

  1. Study on Nanostructures Induced by High-Current Pulsed Electron Beam

    OpenAIRE

    Bo Gao; Yi Hao; Ganfeng Tu; Wenyuan Wu

    2012-01-01

    Four techniques using high-current pulsed electron beam (HCPEB) were proposed to obtain surface nanostructure of metal and alloys. The first method involves the distribution of several fine Mg nanoparticles on the top surface of treated samples by evaporation of pure Mg with low boiling point. The second technique uses superfast heating, melting, and cooling induced by HCPEB irradiation to refine the primary phase or the second phase in alloys to nanosized uniform distributed phases in the ma...

  2. Laser triggered injection of electrons in a laser wakefield accelerator with the colliding pulse method

    OpenAIRE

    Nakamura, K; Fubiani, G; Geddes, C. G. R.; Michel, P.; van Tilborg, J.; Toth, C; Esarey, E.; Schroeder, C. B.; Leemans, W. P.

    2004-01-01

    An injection scheme for a laser wakefield accelerator that employs a counterpropagating laser (colliding with the drive laser pulse, used to generate a plasma wake) is discussed. The threshold laser intensity for electron injection into the wakefield was analyzed using a heuristic model based on phase-space island overlap. Analysis shows that the injection can be performed using modest counterpropagating laser intensity a_1 < 0.5 for a drive laser intensity of a_0 = 1.0. Preliminary expe...

  3. Styrene vapor decomposition in air under the action a pulse electron beam

    CERN Document Server

    Mesyats, G A; Filatov, I E

    2001-01-01

    The results of experiments on the styrene vapor removal from the air through the pulse electron beam of the nanosecond duration and also through the nonindependent voluminous discharge are presented. The macrokinetic equations of the process obtained on the basis of these results, make it possible to systematize the data and also extrapolate them beyond the boundaries of the studied area of concentrations and energy, contained in the gas

  4. A Technique for Temperature and Ultimate Load Calculations of Thin Targets in a Pulsed Electron Beam

    DEFF Research Database (Denmark)

    Hansen, Jørgen-Walther; Lundsager, Per

    1979-01-01

    A technique is presented for the calculation of transient temperature distributions and ultimate load of rotationally symmetric thin membranes with uniform lateral load and exposed to a pulsed electron beam from a linear accelerator. Heat transfer by conduction is considered the only transfer...... mechanism. The ultimate load is calculated on the basis of large plastic strain analysis. Analysis of one aluminum and one titanium membrane is shown....

  5. Measurement of electron density transients in pulsed RF discharges using a frequency boxcar hairpin probe

    Science.gov (United States)

    Peterson, David; Coumou, David; Shannon, Steven

    2015-11-01

    Time resolved electron density measurements in pulsed RF discharges are shown using a hairpin resonance probe using low cost electronics, on par with normal Langmuir probe boxcar mode operation. Time resolution of 10 microseconds has been demonstrated. A signal generator produces the applied microwave frequency; the reflected waveform is passed through a directional coupler and filtered to remove the RF component. The signal is heterodyned with a frequency mixer and rectified to produce a DC signal read by an oscilloscope. At certain points during the pulse, the plasma density is such that the applied frequency is the same as the resonance frequency of the probe/plasma system, creating reflected signal dips. The applied microwave frequency is shifted in small increments in a frequency boxcar routine to determine the density as a function of time. A dc sheath correction is applied for the grounded probe, producing low cost, high fidelity, and highly reproducible electron density measurements. The measurements are made in both inductively and capacitively coupled systems, the latter driven by multiple frequencies where a subset of these frequencies are pulsed. Measurements are compared to previous published results, time resolved OES, and in-line measurement of plasma impedance. This work is supported by the NSF DOE partnership on plasma science, the NSF GOALI program, and MKS Instruments.

  6. Various categories of defects after surface alloying induced by high current pulsed electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Dian [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Tang, Guangze, E-mail: oaktang@hit.edu.cn [School of Material Science & Engineering, Harbin Institute of Technology, Harbin 150001 (China); Ma, Xinxin [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Gu, Le [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Sun, Mingren [School of Material Science & Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, Liqin [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-10-01

    Highlights: • Four kinds of defects are found during surface alloying by high current electron beam. • Exploring the mechanism how these defects appear after irradiation. • Increasing pulsing cycles will help to get good surface quality. • Choosing proper energy density will increase surface quality. - Abstract: High current pulsed electron beam (HCPEB) is an attractive advanced materials processing method which could highly increase the mechanical properties and corrosion resistance. However, how to eliminate different kinds of defects during irradiation by HCPEB especially in condition of adding new elements is a challenging task. In the present research, the titanium and TaNb-TiW composite films was deposited on the carburizing steel (SAE9310 steel) by DC magnetron sputtering before irradiation. The process of surface alloying was induced by HCPEB with pulse duration of 2.5 μs and energy density ranging from 3 to 9 J/cm{sup 2}. Investigation of the microstructure indicated that there were several forms of defects after irradiation, such as surface unwetting, surface eruption, micro-cracks and layering. How the defects formed was explained by the results of electron microscopy and energy dispersive spectroscopy. The results also revealed that proper energy density (∼6 J/cm{sup 2}) and multi-number of irradiation (≥50 times) contributed to high quality of alloyed layers after irradiation.

  7. Time Resolved Measurement of Electron Cloud Densities from Dispersion of Transverse Electric Pulses

    CERN Document Server

    Sonnad, Kiran G

    2015-01-01

    The measurement of electron cloud densities in particle accelerators using microwaves has proven to be an effective, non-invasive and inexpensive method. So far the experimental schemes have used continuous waves. This has either been in the form of travelling waves that are propagated, or standing waves that are trapped, in both cases within a segment of the accelerator chamber. The variation in the wave dispersion relation caused by the periodic creation and decay of the electron cloud leads to a phase modulation in the former case, and a frequency modulation in the latter. In general, these methods enable the measurement of a time averaged electron cloud density. In this paper we propose a time resolved measurement by using pulses propagated over a finite length of the accelerator chamber. The pulses are launched periodically, once after a bunch train has passed and then again half a revolution period later. This results in pulses alternating between a dispersion that is either affected by a cloud or not. ...

  8. Microstructures and properties of zirconium-702 irradiated by high current pulsed electron beam

    Science.gov (United States)

    Yang, Shen; Cai, Jie; Lv, Peng; Zhang, Conglin; Huang, Wei; Guan, Qingfeng

    2015-09-01

    The microstructure, hardness and corrosion resistance of zirconium-702 before and after high-current pulsed electron beam (HCPEB) irradiation have been investigated. The microstructure evolution and surface morphologies of the samples were characterized by using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The experimental results indicate that the sample surface was melted after HCPEB irradiation, and martensitic phase transformation occurred. Besides, two kinds of craters as well as ultrafine structures were obtained in the melted layer. TEM observations suggest that high density dislocations and deformation twins were formed after HCPEB irradiation. With the increasing of pulses, microhardness of the irradiated samples was increased from the initial 178 Hv to 254 Hv. The corrosion resistance was tested by using electrode impedance spectroscopy (EIS) and potentiodynamic polarization curves. Electrochemical results show that, after HCPEB irradiation, all the samples had better corrosion resistance in 1 mol HNO3 solution compared to the initial one, among which the 5-pulsed sample owned the best corrosion resistance. Ultrafine structures, martensitic phase transformation, surface porosities, dislocations and deformation twins are believed to be the dominant reasons for the improvement of the hardness and corrosion resistance.

  9. Dynamical Model in Low-Frequency-Pulsed Electron-Stimulated Desorption

    Institute of Scientific and Technical Information of China (English)

    张彤; 吴小山; 胡安; 毛福明; 杨学谦; 崔一平

    2003-01-01

    A dynamical model of low-frequency=pulsed electron=stimulated desorption is developed. The characteristic of desorbed gas flow is taken as an exponential function, and can be degenerated to a triangular and square wave.The transient pressure is given according to the gas flow of desorbing gas and vacuum system parameters,including the pumping speed and the system volume. Although the mathematical model is deduced from the electron-stimulated desorption, it can be applied to other similar processes of intermittent desorption.

  10. Multipacting saturation in parallel plate and micro-pulse electron gun

    OpenAIRE

    Liao, Lang; ZHANG Meng; Zhao, Minghua

    2014-01-01

    A novel parallel plate model is proposed that divided the electron cloud into three parts at saturation, and it is studied in detail using both an analytical approach and PIC (Particle In Cell) code simulations. As one part of the electron cloud, ribbons modes are suggested by tracking the trajectory of individual particle, and the aim of this mode form is to simplify the progress of multipacting effect in the parallel plate so as to be eliminated by optimizing RF parameters. The micro-pulse ...

  11. Kinetic instabilities in pulsed operation mode of a 14 GHz electron cyclotron resonance ion source

    Energy Technology Data Exchange (ETDEWEB)

    Tarvainen, O., E-mail: olli.tarvainen@jyu.fi; Kalvas, T.; Koivisto, H.; Komppula, J.; Kronholm, R.; Laulainen, J. [Department of Physics, University of Jyväskylä, 40500 Jyväskylä (Finland); Izotov, I.; Mansfeld, D. [Institute of Applied Physics, RAS, 46 Ul‘yanova St., 603950 Nizhny Novgorod (Russian Federation); Skalyga, V. [Institute of Applied Physics, RAS, 46 Ul‘yanova St., 603950 Nizhny Novgorod (Russian Federation); Lobachevsky State University of Nizhny Novgorod (UNN), 23 Gagarina St., 603950 Nizhny Novgorod (Russian Federation)

    2016-02-15

    The occurrence of kinetic plasma instabilities is studied in pulsed operation mode of a 14 GHz A-electron cyclotron resonance type electron cyclotron resonance ion source. It is shown that the temporal delay between the plasma breakdown and the appearance of the instabilities is on the order of 10-100 ms. The most important parameters affecting the delay are magnetic field strength and neutral gas pressure. It is demonstrated that kinetic instabilities limit the high charge state ion beam production in the unstable operating regime.

  12. Ultrafast electron field emission from gold resonant antennas studied by two terahertz pulse experiments

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew C.;

    2015-01-01

    Summary form only given. Ultrafast electron field emission from gold resonant antennas induced by strong terahertz (THz) transient is investigated using two THz pulse experiments. It is shown that UV emission from nitrogen plasma generated by liberated electrons is a good indication of the local...... electric field at the antenna tip. Using this method resonant properties of antennas fabricated on high resistivity silicon are investigated in the strong field regime. Decrease of antenna Q-factor due to ultrafast carrier multiplication in the substrate is observed....

  13. Electron tunnelling through single azurin molecules can be on/off switched by voltage pulses

    Energy Technology Data Exchange (ETDEWEB)

    Baldacchini, Chiara [Biophysics and Nanoscience Centre, DEB-CNISM, Università della Tuscia, I-01100 Viterbo (Italy); Institute of Agro-Environmental and Forest Biology, CNR, I-05010 Porano (Italy); Kumar, Vivek; Bizzarri, Anna Rita; Cannistraro, Salvatore, E-mail: cannistr@unitus.it [Biophysics and Nanoscience Centre, DEB-CNISM, Università della Tuscia, I-01100 Viterbo (Italy)

    2015-05-04

    Redox metalloproteins are emerging as promising candidates for future bio-optoelectronic and nano-biomemory devices, and the control of their electron transfer properties through external signals is still a crucial task. Here, we show that a reversible on/off switching of the electron current tunnelling through a single protein can be achieved in azurin protein molecules adsorbed on gold surfaces, by applying appropriate voltage pulses through a scanning tunnelling microscope tip. The observed changes in the hybrid system tunnelling properties are discussed in terms of long-sustained charging of the protein milieu.

  14. UV pulse trains by α-BBO crystal stacking for the production of THz-rap-rate electron bunches

    Science.gov (United States)

    Yan, Li-Xin; Hua, Jian-Fei; Du, Ying-Chao; Huang, Yuan-Fang; You, Yan; Wang, Dan; Huang, Wen-Hui; Tang, Chuan-Xiang; Tang

    2012-08-01

    Ultrashort electron bunch trains can be used for plasma wake field acceleration (PWFA) to overcome the limit of transformer ratio of a single electron bunch, or high-power terahertz (Thz) radiation production by various radiation mechanisms. Basic facility for high-power THz radiation development based on ultrashort electron beam has been set up at accelerator lab of TUB. Using birefringent crystal serials, ultraviolet (UV) pulse shaping for photocathode radio frequency gun to produce THz-repetition-rate pulse train was realized. Driven by such pulses, ultrashort electron bunch train with picosecond (ps) spacing was obtained for THz production. Measurement of the stacked UV pulse trains was done by difference frequency generation (DFG), and the measured group velocity mismatch of α-BBO crystal at 266.7-nm wavelength was 0.8 ps/mm. This method may also be applied to form ramped electron bunch trains for PWFA.

  15. Surface modification of Al-Pb alloy by high current pulsed electron beam

    Institute of Scientific and Technical Information of China (English)

    LU You; LI Shi-long; AN Jian; LIU Yong-bing

    2006-01-01

    Al-Pb alloy was modified by high current pulsed electron beam and the microstructure, hardness and tribological characteristics were characterized by scanning electron microscopy, electronic microanalysis probe microanalysis, Knoop hardness indentation and pin-on-disc type wear testing machine. The results show that the microstructure and hardness can be greatly improved, and the modification layer consists of a molten zone, an overlapped zone of heat-affected and quasistatic thermal stress-affected zone and a transition zone followed by the substrate. The tribological properties of high current pulsed electron beam irradiated Al-Pb alloy are correspondingly improved largely. Optical observation and scanning electron microscopy analysis reveal that the low wear rate and lowest level in coefficient of friction at high load level for irradiated Al-Pb alloy are due to the formation of a lubricious tribolayer covering the worn surface, which is a mixture of Al2O3, Pb3O4 and silicate. The wear mode varies from oxidative wear at low load to film spalling at high load and, finally, adhesive wear.

  16. Modification of the sample's surface of hypereutectic silumin by pulsed electron beam

    Science.gov (United States)

    Rygina, M. E.; Ivanov, Yu F.; Lasconev, A. P.; Teresov, A. D.; Cherenda, N. N.; Uglov, V. V.; Petricova, E. A.; Astashinskay, M. V.

    2016-04-01

    The article presents the results of the analysis of the elemental and phase composition, defect substructures. It demonstrates strength and tribological characteristics of the aluminium-silicon alloy of the hypereutectic composition in the cast state and after irradiation with a high-intensity pulsed electron beam of a submillisecond exposure duration (a Solo installation, Institute of High Current Electrons of the Siberian Branch of the Russian Academy of Sciences). The research has been conducted using optical and scanning electron microscopy, and the X-ray phase analysis. Mechanical properties have been characterized by microhardness, tribological properties - by wear resistance and the friction coefficient value. Irradiation of silumin with the high-intensity pulsed electron beam has led to the modification of the surface layer up to 1000 microns thick. The surface layer with the thickness of up to 100 microns is characterized by melting of all phases present in the alloy; subsequent highspeed crystallization leads to the formation of a submicro- and nanocrystalline structure in this layer. The hardness of the modified layer decreases with the increasing distance from the surface exposure. The hardness of the surface layer is more than twice the hardness of cast silumin. Durability of silumin treated with a high intensity electron beam is ≈ 1, 2 times as much as the wear resistance of the cast material.

  17. The electron-ion dynamics in ionization of lithium carbide molecule under femtosecond laser pulses

    Science.gov (United States)

    Zhang, Xiaoqin; Wang, Feng; Hong, Xuhai; Su, Wenyong; Gou, Bingcong; Chen, Huimin

    2016-08-01

    The electron-ion dynamics of the linear lithium carbide molecule under femtosecond laser pulses have been investigated in the framework of Ehrenfest molecular dynamics, in which valence electrons are treated quantum mechanically by time-dependent density functional theory (TDDFT) and ions are described classically. The on- and off-resonant multiphoton ionization processes have been induced by regulating laser frequency and laser intensity. The laser pulse with on-resonant frequency induces pronounced enhancement in electron ionization, bond length vibration, and energy absorption. Moreover, the coulomb explosion is preferred to occur in the on-resonant case, which is in qualitative agreement with previous theoretical investigations. The subtle relations between escaped electron number and absorbed photon number are well discussed with the increasing of laser intensity. Finally, the effect of self-interaction error is analyzed by comparing escaped electron number calculated with LDA and LDA-ADSIC. And the revTPSS-meta-GGA, a currently more accurate nonempirical exchange-correlation energy functional from a point of static density functional theory, is introduced to display its capability for the description of ionization process within nonlinear and the nonperturbative regime of isolated systems.

  18. Self-confinement of a fast pulsed electron beam generated in a double discharge

    Energy Technology Data Exchange (ETDEWEB)

    Goktas, H [Ankara Nuclear Research and Training Center, 06501, Besevler, Ankara (Turkey); Udrea, M [National Institute for Laser, Plasma and Radiation Physics, 76900 Bucharest (Romania); Oke, Gulay [Physics Department, Middle East Technical University, 06531 Ankara (Turkey); Alacakir, A [Ankara Nuclear Research and Training Center, 06501, Besevler, Ankara (Turkey); Demir, A [Physics Department, University of Kocaeli, 41200 Kocaeli (Turkey); Loureiro, J [Centro de Fisica dos Plasmas, Instituto Superior Tecnico, 1049-001 Lisbon (Portugal)

    2005-08-21

    The construction of a double discharge pulsed electron beam generator and the study of the characteristics of the beam are presented in this paper. The electron beam generator consists of a fast filamentary discharge in superposition with an ordinary glow discharge in low-pressure gases. The filling gas is argon or helium at approximately 0.1 Torr pressure. The duration of the electron beam is shorter than 50 ns and the peak current intensity is of the order of amperes. The electron density is evaluated by making use of Stark broadening of the H{sub {beta}} line and compared with the full computer simulation method. The pinch effect of the filamentary discharge is evaluated and its size compared with the diameter of the beam.

  19. Ultrafast dynamics driven by intense light pulses from atoms to solids, from lasers to intense X-rays

    CERN Document Server

    Gräfe, Stefanie

    2016-01-01

    This book documents the recent vivid developments in the research field of ultrashort intense light pulses for probing and controlling ultrafast dynamics. The recent fascinating results in studying and controlling ultrafast dynamics in ever more complicated systems such as (bio-)molecules and structures of meso- to macroscopic sizes on ever shorter time-scales are presented. The book is written by some of the most eminent experimental and theoretical experts in the field. It covers the new groundbreaking research directions that were opened by the availability of new light sources such as fully controlled intense laser fields with durations down to a single oscillation cycle, short-wavelength laser-driven attosecond pulses and intense X-ray pulses from the upcoming free electron lasers. These light sources allowed the investigation of dynamics in atoms, molecules, clusters, on surfaces and very recently also in nanostructures and solids in new regimes of parameters which, in turn, led to the identification of...

  20. Improved wear resistance of Al-15Si alloy with a high current pulsed electron beam treatment

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Y. [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Gao, B., E-mail: surfgao@yahoo.com.cn [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Tu, G.F.; Li, S.W. [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Dong, C. [Key Laboratory of the Ministry of Education of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Dalian 116024 (China); Zhang, Z.G. [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China)

    2011-07-01

    Highlights: > Firstly, Raman spectra are used to research the variation of Si structure before and after HCPEB treatment for the first time. > Secondly, a fine structure, namely the precipitation of nanocrystalline Si particles, is formed in the surface layer of the HCPEB-treated sample. > Thirdly, the relative wear resistance of an Al-15Si alloy surface is effectively enhanced by a factor of 9 after 15 pulse treatment. - Abstract: A hypereutectic Al-15Si alloy (Si 15 wt.%, Al balance) was irradiated by high current pulsed electron beam (HCPEB). The HCPEB treatment causes ultra-rapid heating, melting and cooling at the top surface layer. As a result, the special 'halo' microstructure centering on the primary Si phase is formed on the surface due to interdiffusion of Al and Si elements. The composition of the 'halo' microstructure is distributed continuously from the center to the edge of the 'halo'. Compared to an untreated matrix, the remelted layer underneath the surface presents single contrast because of the compositional homogeneity after HCPEB treatment. The thickness of the remelted layer increases slightly from 4.4 {mu}m (5 pulses) to 5.6 {mu}m (25 pulses). HCPEB treatment broadens and shifts the diffraction peaks of Al and Si. The lattice parameters of Al decreases due to the formation of a supersaturated solid solution of Al in the melted layer. Through analysis of Raman spectra and transmission electron microscopy (TEM), the amorphous Si (a-Si) and nanocrystalline Si are formed in the near-surface region under multiple bombardments of HCPEB. The relative wear resistance of a 15-pulse sample is effectively improved by a factor of 9, which can be attributed to the formation of metastable structures.