free-electron laser electron injector

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Laser heater commissioning at an externally seeded free-electron laser

Laser heater commissioning at an externally seeded free-electron laser

chromatic dispersion, the MBI induces a broadband modu- lation of the electron beam energy and longitudinal charge distribution. This process originates with shot noise and cathode-induced nonuniformities in the particle distribution and is further stimulated and amplified by any downstream energy or charge density modulation, e.g., space charge forces in the low energy injector region, nonzero longi- tudinal impedance in the rf accelerator cells and drift sections, and the strong chromatic dispersion sections associated with magnetic bunch length compressors that increase the electron bunch peak current to the level required for photon production. Coherent synchrotron radiation (CSR) in these bunch compressors can further enhance the MBI-induced energy and density modulations [3,4]. At the undulator entrance, the electron beam can have significant longitudinal energy and density modulations [1,5,6] on the multimicron to submicron scale lengths. The longer wavelength modulations can degrade the FEL spectrum, especially for a seeded source, while those at the shortest wavelengths effectively appear as an increased “ slice ” energy spread that can reduce the FEL gain and output radiation intensity.
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Electrochemical Preparation of Particles for X-Ray Free Electron Laser Based Diffractive Imaging

Electrochemical Preparation of Particles for X-Ray Free Electron Laser Based Diffractive Imaging

The FERMI X-ray Free Electron Laser (XFEL) at Elettra will be a powerful tool of investigation in new fields of materials science, based on ultrashort EUV pulses. Among cutting-edge applications, diffractive imaging of nano- and microparticles is a specially hot topic. In this field, the particle- injection approach is regarded as optimal in terms of imaging quality. The possibility of pre-treating the particles with electrochemical approaches at the insertion station is expected to offer additional flexibility for users. Electrochemical modification of the particles can be straightforwardly obtained by the bipolar approach and extraction of a particle stream into the injector will safely occur in times allowing the possibility of studying intact electrochemical double layers according to the electrode- emersion method. In this paper, a first section is dedicated to: (i) the definition of a mathematical model describing the bipolar electrochemical behavior of particles; (ii) its implementation in a finite element analysis package; (iii) the discussion of results of numerical simulations, allowing to predict the effects of relevant process parameters. In a second section, the experimental part is described, consisting in: (i) the fabrication of a packed-bed and a fluidised-bed electrochemical reactor, able to support the bipolar electrochemical operation of micrometric particles; (ii) the treatment in aqueous environment of Cu and WC particles; (iii) the characterisation by SEM and XRD of the treated powders, in order to pinpoint surface changes induced by the electrochemical process.
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A high average current electron source for the Jefferson Laboratory free electron laser

A high average current electron source for the Jefferson Laboratory free electron laser

Injector design is rather time intensive as the computation time for each simula- tion can be long (hours, depending on complexity), even with the faster codes. These simulations then need to be repeated for many different conditions. Par- allel processing can ease the burden somewhat, by computing a number of solu- tions simultaneously. Evolutionary algorithms naturally lend themselves to the use of parallel processing, as a population of trial solutions can be calculated each on an individual processor. Only after each trial solution has been com- puted is there a need to compile the information for selection for the mating pool, crossing and mutation. The optimisation program developed at Cornell used this procedure. The algorithm was based on a modified version of PISA [125] (Platform and programming language independent Interface for Search Algorithms), developed at the Institute of Technology, Zurich (ETH) [126]. PISA separates the optimisation problem into two modules. One part, called the vari- ator, contains those things specific to the optimisation problem. For example
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Spatial Meaning of Quantum Mechanics

Spatial Meaning of Quantum Mechanics

energy and energy transformation without the necessity of dealing with the force directly. The energy does not belong to the electron alone, but both the electron and the electric field. For Schrödinger equation, it is an inappropriate perspective to separate the electron from the Hamiltonian and assign the energies only to the electron, regardless of the electric field. A space consisting of electron and electric field is different from vacuum, and such a space may be called a field. As such, it is the space (or the field) rather than the electron exhibits a wave phenomenon. The wave like light wave can be made quantization to give particles, none of which is the electron that is a material particle. It can be understood since de Broglie’s work antedated Schrödinger equation and Dirac radiation field theory, and his postulate was not able to ascribe the wave properties to the space containing electrons. It is the continuous mo- tion of the electron that causes the wave. It seems that Schrödinger did not perceive that the wave originates in the electron’s motion, and the wave functions can change with time even if for a steady system. The wave mo- tion requires each wave function to vibrate at its own site. The wave hence is a disturbance of the wave func- tions in the space. A wave function at a position transfers its physical state in this way to the wave function at the next position. The wave as a whole is to be made quantization to produce particles to be like photons. Even though Schrödinger equation for single electron gives perfectly accurate solution, there is still more or less defi- ciency of dynamical characteristics for the wave functions. His time-dependent wave equation is a second-order differential in the three spatial coordinates but only a first-order differential in time. Actually, the wave motion is a classical phenomenon satisfying a classical dynamical equation with a second-order differential in time. In addition, the wave function of a system of N electrons is a function in a 3N-dimensional configuration space, in which the Born’s probabilistic interpretation cannot be used. It is difficult to imagine that a physical reality ex- ists in such an abstract multidimensional configuration space. The double-slit experiment is a successful exam- ple of the probabilistic interpretation [14] [20]. The behavior of an electron in the space between the slit and the detector shows the characteristics of a free electron. For these reasons, in the third section of this paper, the wave functions for the space involving a free electron are obtained by means of a dynamical equation. Then, the wave quantization for such space will be made, which will give a theoretical evidence of the probabilistic inter- pretation. In the fourth section we discuss different meanings of wave-particles for photons and for electron. The relativistic effect will not be discussed in this paper.
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A Review Study on Amplification of X Ray Free Electron Laser Pulse in Plasma

A Review Study on Amplification of X Ray Free Electron Laser Pulse in Plasma

[23,24] results has shown the possibility and potential to focus and compress the intense laser pulses (optical and X-ray regime) through Backward Raman amplification (BRA) in plasmas. We report here the review study of these results and similar scalings for efficient BRA to compress and amplify the intense X-ray pulse. Before explaining the review work we outline first the BRA process in plasmas. BRA is based on the fact that a plasma can withstand very high energy densities due to its ionized nature. This has motivated research to realize a plasma amplifier to further boost the power of an ex- isting CPA system [25] or as an alternative technique that will replace CPA itself [26]. The idea of the Raman ef- fect in various media to amplify laser pulses extends back to work carried out 40 years ago when researchers used gases and liquids to amplify excimer laser pulses for the purpose of laser-based nuclear fusion [27]. The idea of using plasmas for this same purpose is however more recent. Proof-of-principle experiments demonstrating BRA in a plasma have been reported by several groups over the last 10 years. These studies have focused primarily on the amplification of ultrashort Ti:Sapphire laser pulses with the goal of creating ultrahigh peak intensities by significantly increasing the amount of energy contained in a single femtosecond-scale pulse.
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Serial Femtosecond X-ray Diffraction of HIV-1 Gag MA-IP6 Microcrystals at Ambient Temperature

Serial Femtosecond X-ray Diffraction of HIV-1 Gag MA-IP6 Microcrystals at Ambient Temperature

microcrystals in liquid suspension at ambient temperature using an X-ray free-electron laser. MicroED opens a new era for biological structure determination[r]

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A wide bandwidth free-electron laser with mode locking using current modulation

A wide bandwidth free-electron laser with mode locking using current modulation

Although the basics of the FEL mode-locking theory match well with conventional laser theory, differences remain. In the conventional atomic laser oscillator, the gain of the radiation signal during one round-trip is relatively small and a buildup of the laser power occurs over a large number of round-trips. This is why mode locking is typically obtained when the laser is at, or near, saturation (the transient period of signal growth is not important). However, in the high-gain FEL amplifier considered here, the gain in each undulator/chicane module may be significantly larger than the round-trip gain of a conventional laser oscillator, and strong mode-coupling develops in the linear regime during exponential growth. The high-gain FEL interaction may be approximated by inserting an exponential amplitude gain factor e α into the wave form of the field equation (8) to obtain:
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Sample Pages. Andreas Gebhardt. Understanding Additive Manufacturing. Rapid Prototyping - Rapid Tooling - Rapid Manufacturing

Sample Pages. Andreas Gebhardt. Understanding Additive Manufacturing. Rapid Prototyping - Rapid Tooling - Rapid Manufacturing

While the standard plastic material is a polyamide of the PA11 or PA12 type, today’s cutting edge materials mimic the properties of PC, ABS, PA (6.6) plastics and deliver parts that show engineering design elements, such as film-hinges and snap-fits. Although the high temperature system EOS 395 (2011) is currently the only commercial system that processes even high performance plastics (PEEK,) it marks a future trend. Materials for laser sintering are available unfilled or filled with spherical or egg-shaped glass, aluminum, or carbon particles in order to improve the stability and heat deflec- tion temperature. Even flame-retarding materials are available.
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Spectroscopic Characterization of the Product Ions Formed by Electron Ionization of Adamantane

Spectroscopic Characterization of the Product Ions Formed by Electron Ionization of Adamantane

Electron ionization of adamantane produces a prominent mass peak at m/z 79 (see Figure 1). An obvious candidate structure for this fragment is protonated benzene, but alternative structures are not a priori impossible. Therefore, an IRMPD spectrum was recorded for this ion. IR induced dissociation of this fragment ion yields only a single product at m/z 77, presumably by H 2 loss. The IRMPD spectrum of m/z 79 is shown in Figure 2 together with the computed spectrum of proto- nated benzene and the match between the measured and computed spectrum is convincing. Other isomers such as 1- and 2-protonated fulvene (at + 39.3 and + 108.7 kJ/mol relative to protonated benzene, respectively) and the methyl-substi- tuted cyclopentadienyl cation (+ 137.1 kJ/mol) do not match the recorded spectrum (see SI Figure S1). The m/z 79 fragment ion can thus be securely identified as protonated benzene.
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The quantum free electron laser

The quantum free electron laser

Free-electron lasers (FELs) have demonstrated the ability to produce coherent radiation ranging from the microwave to the X-ray region of the electromagnetic spectrum. Although the first theoretical studies of the FEL involved a quantum mechanical analysis (e.g., [1]), it is generally accepted that FEL experiments to date are well described by classical models in which an electron beam consisting of classical particles interacts with a classical electromagnetic radiation field. Until relatively recently, most theoretical studies using a quantum analysis have been restricted to the regime of low gain (e.g., [2–6]). More recently, however, there has been a revival of interest in the role of quantum effects in the FEL interaction (e.g., [7–9]), stimulated in part by the development of short-wavelength, high-gain FEL amplifiers producing progressively higher-energy photons (see, e.g., Ref. [10] for a review of X-ray FELs). In this article, methods for describing the quantum regime of high-gain FEL operation are outlined and some of the effects which are beyond description by the usual classical models are discussed.
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Herrwerth, Oliver
  

(2011):


	Atomic and molecular ionization dynamics in strong IR and XUV fields probed by time-resolved coincidence spectroscopy.


Dissertation, LMU München: Fakultät für Physik

Herrwerth, Oliver (2011): Atomic and molecular ionization dynamics in strong IR and XUV fields probed by time-resolved coincidence spectroscopy. Dissertation, LMU München: Fakultät für Physik

Decades of research with intense optical lasers and synchrotron radiation established dedicated experimental tools for investigation of multiple ionization and fragmentation processes in atoms and molecules. Starting with measuring intensity-dependent ion yields and total ionization cross sections respectively and continuing with measurements of sin- gle or multiple differential cross sections, instrumental progress recently culminated in experiments yielding fully differential data for fragmentation of simple atomic [17, 74– 76] and molecular [77–80] systems. Here, a major step was achieved with the invention of coincident cold-target recoil-ion and electron momentum spectroscopy. These spec- trometers (sometimes called ”reaction microscopes” [81–84]), based on combined electric- and magnetic-field projection techniques, time- and position-sensitive micro-channel plate (MCP) detectors and supersonic gas jets providing cold atomic or molecular targets, al- lowed for the simultaneous and coincident measurement of the full 3D momentum vectors for several charged reaction fragments (the so-called kinematically complete experiments). Due to the fact that the fragments are imaged with a large (often reaching 4π) solid angle, in many cases these spectrometers enabled recording complete probability densities of the final many-particle momentum states. This, along with the possibility of reliable back- ground elimination procedures applying momentum conservation conditions [84, 85] gener- ating remarkable clean spectra, made this technique extremely successful in time-resolved experiments [69, 70, 86–90]. Because of its capabilities to separate different reaction chan- nels leading to the same final states and cleanly revealing even weak ionization pathways based on the energy- and angular-resolved many particle detection, this approach has now become a state of the art technique for FEL [36, 37, 40–44, 91] and HHG [69, 70] based atomic and molecular research.
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Tungsten oxide-Au nanosized film composites for glucose oxidation and sensing in neutral medium

Tungsten oxide-Au nanosized film composites for glucose oxidation and sensing in neutral medium

catalyst dispersion and its durability against sintering and particle aggregation. MOx can also promote certain electrocatalytic reactions via electronic effect or even function as cocatalysts via a bifunctional mechanism. In addition, several MOx possess high isoelectric points (9) and can be helpful to immobilize through electrostatic interactions enzymes with low isoelectric points, which helps to retain the bioactivity of the enzyme – an important issue for mediator-free enzymatic electrodes for biological fuel cells. 5

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Electron Density Measurement by Raman Calibration of the HuanLiuqi-2A Thomson Scattering System

Electron Density Measurement by Raman Calibration of the HuanLiuqi-2A Thomson Scattering System

A single point TS measuring system [15], as shown in Fig. 1, is developed for HL-2A tokamak, in which a high energy Nd-doped yttrium aluminum garnet (Nd:YAG) laser is used. The Nd:YAG laser is composed of one oscil- lator and three stage amplifiers. Its main parameters are wavelength of 1064 nm, pulse width of about 10 ns, beam diameter of 30 mm, pulse energy of 6 J at 1 Hz or 5 J at 5 Hz or 4 J at 10 Hz depending on di ff erent repetition rate, and 4 J at 10 Hz is the normal working conditions. The Nd:YAG laser beam is infrared and short pulsed, for its alignment, we use a visible green laser beam of 30 mm also in diameter and a 2-color filter, which highly reflects the green beam and transmits the infrared beam with 45 ◦ incidence angle. The both two beams are adjusted to travel horizontally along the same axis and then delivered into input optics. At there, a mirror reflects them upwards and an f = 5 m lens focuses them into the vacuum chamber from the bottom to the top. Because the throat passage of HL-2A lower divertor is curved and very narrow, it is important to allow the YAG laser beam to traverse the ma- chine without any risk to damage it. So behind the output window, a TV camera is used to monitor the position of the green beam, which is checked to be co-axis with the in- frared laser beam. Though careful alignments are made for the laser beams, the strayed laser light is very strong and it is confirmed to be produced mainly from the lower and up- per divertor throats when the YAG laser passing through. While in other TS systems [1, 2], the strayed laser light is
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Echo enabled harmonic generation free electron laser in a mode-locked configuration

Echo enabled harmonic generation free electron laser in a mode-locked configuration

The method of EEHG manipulates electron pulse phase space using two temporally coherent, long wavelength seed lasers and two dispersive chicanes. The electrons are first modulated by a seed laser in an undulator and then dispersed in a chicane. This process is then repeated and a fine microbunching of the electron beam is created at a shorter wavelength while retaining a high level of the temporal coherence from the long wavelength lasers. When propagated through a final radiator undulator, the electron beam emits X-rays at the shorter wavelength of the electron microbunching and with an improved temporal coherence over that generated by self-amplified spontaneous emission which starts from intrinsic shot- noise in the electron beam [13]. Previous models of EEHG have used periodic boundary conditions applied to the electron phase space and simulation codes that average the electron and radiation properties over a radiation wavelength.
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Electromagnetic field measurements inside photonic crystals developing a photonic free electron laser

Electromagnetic field measurements inside photonic crystals developing a photonic free electron laser

Furthermore, waveguides and PhC allow many modes of operation. Some of these modes have strong maxima in the center of the PhC, others have nodes. Fig. 2.9 shows two possible transverse mode patterns of the E z - field. The red line plots the transverse field pattern of the E -field at a fixed position taken along the width-axis x of the PhC. A blue electron is drawn to denote x-position of the electron beam. As seen in fig. 2.9(a), the electron beam in the spFEL propagates exactly at the maximum of the mode-pattern. This allows strong interaction and gain. In fig. 2.9(b) the mode-pattern has a node exactly at the beam path. Electrons have a very weak interaction and generate no gain.
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Femtosecond Laser Pulse Train Effect on Optical Characteristics and Nonequilibrium Heat Transfer in Thin Metal Films

Femtosecond Laser Pulse Train Effect on Optical Characteristics and Nonequilibrium Heat Transfer in Thin Metal Films

Figure 2 depicts the transient variations in reflectivity and laser intensity at the top surface for the single and two-pulse trains. In both cases, the reflectivity at the early stage of laser exposure decreased considerably because the collision frequencies and the dielectric functions changed with an abrupt increase in electron temperature during laser irradi- ation with high peak power and a very short pulse. Figure 2(b) shows that the effective laser intensity of the first pulse was lower than that of the second pulse because of the decrease in reflectivity from 93 to 75% during laser irradiation. It indicates that, prior to the second pulse, the film properties had already changed due to the heating by the first pulse. This change is demonstrating that the optical characteristics for pulse train laser are different from that using the single pulse laser, and in turn, the decrease in reflectivity can increase the absorption of photon energy and affect the ablation process in thin films.
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Diagnostic Study of Nickel Plasma Produced by Fundamental (1064 nm) and Second Harmonics (532 nm) of an Nd: YAG Laser

Diagnostic Study of Nickel Plasma Produced by Fundamental (1064 nm) and Second Harmonics (532 nm) of an Nd: YAG Laser

slope equal to (−1/kT). Thus the electron temperature can be determined without the knowledge of the total number density or the partition function. Errors are bound to be present in the determination of the electron temperature by this method therefore; the electron temperature is de- termined with ≈10% uncertainty, coming mainly from the transition probabilities and the measurement of the integrated intensities of the spectral lines. The line iden- tifications and different spectroscopic parameters such as wavelength (λ), statistical weight (g), transition probabil- ity (A) and term energy (E) listed in the Table 1.
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Proton driven plasma wakefield acceleration in AWAKE

Proton driven plasma wakefield acceleration in AWAKE

The laser pulse is additionally used to seed the self-modulation process. In principle, the self- modulation of a long proton bunch can grow from the random noise in a preformed plasma. Then, the wakefields phase and amplitude varies from event to event and controlled electron injection (into the accelerating, focusing phase) is not possible. To fix the wakefields phase and amplitude, we seed the self-modulation process: we overlap the laser pulse in space and time with the proton bunch. The laser pulse creates an ionization front (see bottom panels on Fig. 1) inside the proton bunch. Protons ahead of the laser pulse propagate in rubidium vapor, the ones after in the plasma (the transition is sharp due to the short length of the laser pulse). Figure 2 shows the initial transverse and longitudinal seed fields along the proton bunch at the plasma entrance for when it is seeded sharply at the center. We note that this initial wakefield amplitudes (W r ) are
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The application of extreme ultra-violet lasers in plasma heating and diagnosis

The application of extreme ultra-violet lasers in plasma heating and diagnosis

Laser-plasma studies have been undertaken for 50 years using infra-red to ultra-violet lasers. We show that a new regime of laser-produced plasmas can be created with capillary discharge and free electron lasers operating in the extreme ultra-violet (EUV). For example, EUV radiation (wavelength < 50 nm) has a critical electron density above electron densities formed by ionization at solid material density and so potentially can penetrate to large depth into a solid density plasma. We explore here the importance of this penetration in ablating solid targets, in creating novel warm dense matter and in the diagnosis of plasmas.
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Synchrotron Infrared Microscopy Analysis of Amyloid Fibrils Irradiated by Mid Infrared Free Electron Laser

Synchrotron Infrared Microscopy Analysis of Amyloid Fibrils Irradiated by Mid Infrared Free Electron Laser

We have recently found that a free-electron laser (FEL) tuned to the amide I band (1600 - 1700 cm −1 ) is able to dissociate the amyloid fibrils of lysozyme and of a five-residue peptide (DFNKF) of the thyroid hormone [8] [9]. In the case of lysozyme fibrils, the β -sheet content of the fibrils diminishes, and the enzyme can be refolded into the active form after the FEL irradiation [8]. FEL can deliver picosecond pulses, high-photon density, and high-power radiation [10]-[14], and it can be suggested that non-covalent bonds such as hydrogen bonds be- tween the β -sheet structures of amyloid fibrils are cleaved by the high-powered pulsed laser tuned to the fre- quency of amide C=O stretching vibration to induce the disaggregation of amyloid fibrils [8]. The structural change was determined by using conventional Fourier transform infrared (FTIR) spectroscopy in the previous study. In the case of the short peptide, however, FTIR spectroscopy could not determine the conformational changes in detail because the peptide has several conformations and a flexible structure in solution [9]. X-ray crystallography and nuclear magnetic resonance (NMR) are usually employed to determine the structure of pep- tides [15]-[17], but while these analytical methods are excellent for three-dimensional structural determination at the atomic level, they are also time consuming, and once analyzed, samples cannot be re-used for other analyti- cal methods. In contrast, IR absorption spectral measurements are comparatively simple, and the spectra are sensitive to the secondary structures of the peptides [18]. Moreover, the normal structure of a peptide can be easily distinguished from the amyloid fibril structure in IR spectra because a peak of the amide I band shifts to as smaller wavenumber as the content of β -sheet structure increases during fibrillation of the peptide [19] [20]; IR absorption measurements are therefore also useful for detecting amyloid
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