First Observations of Laser-Driven Acceleration of Relativistic Electrons in a Semi-Infinite Vacuum Space PDF Download
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Author: J. E. Spencer
Publisher:
ISBN:
Category :
Languages : en
Pages : 3
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Book Description
We have observed acceleration of relativistic electrons in vacuum driven by a linearly polarized visible laser beam incident on a thin gold-coated reflective boundary. The observed energy modulation effect follows all the characteristics expected for linear acceleration caused by a longitudinal electric field. As predicted by the Lawson-Woodward theorem the laser driven modulation only appears in the presence of the boundary. It shows a linear dependence with the strength of the electric field of the laser beam and also it is critically dependent on the laser polarization. Finally, it appears to follow the expected angular dependence of the inverse transition radiation process. experiment as the Laser Electron Accelerator Project (LEAP).
Author: J. E. Spencer
Publisher:
ISBN:
Category :
Languages : en
Pages : 3
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Book Description
We have observed acceleration of relativistic electrons in vacuum driven by a linearly polarized visible laser beam incident on a thin gold-coated reflective boundary. The observed energy modulation effect follows all the characteristics expected for linear acceleration caused by a longitudinal electric field. As predicted by the Lawson-Woodward theorem the laser driven modulation only appears in the presence of the boundary. It shows a linear dependence with the strength of the electric field of the laser beam and also it is critically dependent on the laser polarization. Finally, it appears to follow the expected angular dependence of the inverse transition radiation process. experiment as the Laser Electron Accelerator Project (LEAP).
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 12
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Book Description
We recently achieved the first experimental observation of laser-driven particle acceleration of relativistic electrons from a single Gaussian near-infrared laser beam in a semi-infinite vacuum. This article presents an in-depth account of key aspects of the experiment. An analysis of the transverse and longitudinal forces acting on the electron beam is included. A comparison of the observed data to the acceleration viewed as an inverse transition radiation process is presented. This is followed by a detailed description of the components of the experiment and a discussion of future measurements.
Author: J. E. Spencer
Publisher:
ISBN:
Category :
Languages : en
Pages : 34
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Author: Liang Jie Wong
Publisher:
ISBN:
Category :
Languages : en
Pages : 88
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Book Description
I first review basic models for laser-plasma interaction that explain electron acceleration and beam confinement in plasma. Next, I discuss ponderomotive electron acceleration in infinite vacuum, showing that the transverse scattering angle of the accelerated electron may be kept small with a proper choice of parameters. I then analyze the direct (a.k.a. linear) acceleration of an electron in infinite vacuum by a pulsed radially-polarized laser beam, consequently demonstrating the possibility of accelerating an initially-relativistic electron in vacuum without the use of ponderomotive forces or any optical devices to terminate the laser field. As the Lawson-Woodward theorem has sometimes been cited to discount the possibility of net energy transfer from a laser pulse to a relativistic particle via linear acceleration in unbounded vacuum, I derive an analytical expression (which I verify with numerical simulation results) defining the regime where the Lawson-Woodward theorem in fact allows for this. Finally, I propose a two-color laser-driven direct acceleration scheme in vacuum that can achieve electron acceleration exceeding 90% of the one-color theoretical energy gain limit, over twice of what is possible with a one-color pulsed beam of equal total energy and pulse duration.
Author: T. Plettner
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Book Description
This article calculates the energy gain of a single relativistic electron interacting with a single gaussian beam that is terminated by a metallic reflector at normal incidence by two different methods: the electric field integral along the path of the electron, and the overlap integral of the transition radiation pattern from the conductive foil with the laser beam. It is shown that for this instance the two calculation methods yield the same expression for the expected energy change of the electron.
Author: R. Bonifacio
Publisher: Elsevier
ISBN: 0444598723
Category : Science
Languages : en
Pages : 326
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Book Description
During the past few years the physics and technology of charged particle beams on which electron-positron linear colliders in the TeV region, storage rings from synchrotron radiation sources and Free Electron Lasers are based, has seen a remarkable development. The purpose of this series of schools is to address the physics and technology issues of this field, train young people and at the same time provide a forum for discussions on recent advances for scientists active in this field. The subjects chosen for this first course reflect the recent interest in TeV electron positron colliders, the possibility offered by Free Electron Lasers to power them and the developments in the production of high brightness electron beams.
Author: Tomas Plettner
Publisher:
ISBN:
Category :
Languages : en
Pages : 160
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Book Description
Author: Drew Pitney Higginson
Publisher:
ISBN: 9781267908506
Category :
Languages : en
Pages : 156
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Book Description
The cone-guided fast ignition approach to Inertial Confinement Fusion requires laser-accelerated relativistic electrons to deposit kilojoules of energy within an imploded fuel core to initiate fusion burn. One obstacle to coupling electron energy into the core is the ablation of material, known as preplasma, by laser energy proceeding nanoseconds prior to the main pulse. This causes the laser-absorption surface to be pushed back hundreds of microns from the initial target surface; thus increasing the distance that electrons must travel to reach the imploded core. Previous experiments have shown an order of magnitude decrease in coupling into surrogate targets when intentionally increasing the amount of preplasma. Additionally, for electrons to deposit energy within the core, they should have kinetic energies on the order of a few MeV, as less energetic electrons will be stopped prior to the core and more energetic electrons will pass through the core without depositing much energy. Thus a quantitative understanding of the electron energy spectrum and how it responds to varied laser parameters is paramount for fast ignition. For the first time, this dissertation quantitatively investigates the acceleration of electrons using an ultra-high-contrast laser. Ultra-high-contrast lasers reduce the laser energy that reaches the target prior to the main pulse; drastically reducing the amount of preplasma. Experiments were performed in a cone-wire geometry relevant to fast ignition. These experiments irradiated the inner-tip of a Au cone with the laser and observed electrons that passed through a Cu wire attached to the outer-tip of the cone. The total emission of K[alpha] x-rays is used as a diagnostic to infer the electron energy coupled into the wire. Imaging the x-ray emission allowed an effective path-length of electrons within the wire to be determined, which constrained the electron energy spectrum. Experiments were carried out on the ultra-high-contrast Trident laser at Los Alamos National Laboratory and at the low-contrast Titan laser at Lawrence Livermore National Laboratory. The targets were irradiated using these 1.054 [mu]m wavelength lasers at intensities from 1019 to 1020 W/cm2. The coupling of energy into the Cu wire was found to be 2.7x higher when the preplasma was reduced using high-contrast. Additionally, higher laser intensity elongated the effective path-length of electrons within the wire, indicating that their kinetic energy was higher. To understand the physics behind laser-acceleration of electrons and to examine how this mechanism is affected by the presence of preplasma, simulations were performed to model the laser interaction. This simulations modeled the interaction using a 0.1 to 3 [mu]m exponential preplasma scale length for the high-contrast cases and hydronamically simulated longer scale preplasma (~25 [mu]m) for the low-contrast case. The simulations show that absorption of laser light increases from only 20% with a 0.1 [mu]m scale length to nearly 90% with a long low-contrast-type preplasma. However, as observed in experiments, a smaller fraction of this absorbed energy is transported to the diagnostic wire, which is due to an increased distance that the electrons must travel to reach the wire and increase angular divergence of the electrons. The simulations show that increasing the preplasma scale length from 0.1 to 3 [mu]m increases the average energy by a factor of 2.5x. This is consistent with an increased interaction length over which the electrons can gain energy from the laser. The simulated electrons are compared with experimental data by injecting them into another simulation modeling the transport of electrons through the cone-wire target. This method quantitatively reproduced the experimentally measured the K[alpha] x-ray emission profiles in the high-contrast cases, which gives confidence in the simulations and the generated electron distributions. By showing that the reduction of preplasma increases coupling into surrogate targets this work shows a significant advantage for the fast ignition scheme. Such work gives confidence to facilities that increasing the contrast of their laser systems will increase electron coupling. Additionally, detailed investigation of these high-contrast systems will aid researchers in understanding the effect that preplasma has on the acceleration of electrons.
Author: Karl Schmid
Publisher: Springer Science & Business Media
ISBN: 364219950X
Category : Science
Languages : en
Pages : 169
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Book Description
This thesis covers the few-cycle laser-driven acceleration of electrons in a laser-generated plasma. This process, known as laser wakefield acceleration (LWFA), relies on strongly driven plasma waves for the generation of accelerating gradients in the vicinity of several 100 GV/m, a value four orders of magnitude larger than that attainable by conventional accelerators. This thesis demonstrates that laser pulses with an ultrashort duration of 8 fs and a peak power of 6 TW allow the production of electron energies up to 50 MeV via LWFA. The special properties of laser accelerated electron pulses, namely the ultrashort pulse duration, the high brilliance, and the high charge density, open up new possibilities in many applications of these electron beams.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 39
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Book Description
This paper discusses some of the important issues pertaining to laser acceleration in vacuum, neutral gases and plasmas. The limitations of laser vacuum acceleration as they relate to electron slippage, laser diffraction, material damage and electron aperture effects, are discussed. An inverse Cherenkov laser acceleration configuration is presented in which a laser beam is self guided in a partially ionized gas. Optical self guiding is the result of a balance between the nonlinear self focusing properties of neutral gases and the diffraction effects of ionization. The stability of self guided beams is analyzed and discussed. In addition, aspects of the laser wakefield accelerator are presented and laser driven accelerator experiments are briefly discussed.
