Generation, Acceleration and Measurement of Attosecond Electron Beams from Laser-plasma Accelerators PDF Download
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Author: Maria Katharina Weikum
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Languages : en
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Author: Maria Katharina Weikum
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Languages : en
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Author: Satomi Shiraishi
Publisher: Springer
ISBN: 3319085697
Category : Science
Languages : en
Pages : 133
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This thesis establishes an exciting new beginning for Laser Plasma Accelerators (LPAs) to further develop toward the next generation of compact high energy accelerators. Design, installation and commissioning of a new experimental setup at LBNL played an important role and are detailed through three critical components: e-beam production, reflection of laser pulses with a plasma mirror and large wake excitation below electron injection threshold. Pulses from a 40 TW peak power laser system were split into a 25 TW pulse and a 15 TW pulse. The first pulse was used for e-beam production in the first module and the second pulse was used for wake excitation in the second module to post-accelerate the e-beam. As a result, reliable e-beam production and efficient wake excitation necessary for the staged acceleration were independently demonstrated. These experiments have laid the foundation for future staging experiments at the 40 TW peak power level.
Author: Kay-Uwe Amthor
Publisher:
ISBN: 9783833470875
Category :
Languages : en
Pages : 120
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In order to accelerate charged particles, electric fields have to be applied. The highest electric fields reached in radio frequency particle accelerators are of the order of 10 MV/m. This field poses an upper limit for conventional accelerator technology because for higher fields the electrodes will be ionized. What if this limit is circumvented and the electric field is build up in an already ionized medium? The idea of using laser generated plasmas for particle acceleration has been conceived about 25 years ago, and is currently a very active and fascinating subject in theoretical and experimental physics. In a plasma the maximum attainable electric fields are of the order of 1000 GV/m, five orders of magnitude larger than for RF accelerators. The dimensions to generate high energy particles shrink from kilometers to millimeters. Therefore, laser plasma acceleration may become an attractive future option for particle acceleration. In this work experimental contributions to the generation of particle beams from laser plasmas are presented. Electron beams with improved parameters, and the first quasi monoenergetic proton beams have been generated and investigated utilizing a compact table top laser system at the Jena laser facility. These experiments are described and discussed in this book.
Author: Salima Abuazoum
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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This thesis addresses two important topics in the field of laser-driven plasma accelerators. Firstly, the research investigates the generation of relativistic electron beams through laser-wakefield acceleration (LWFA) by applying novel tapered capillary discharge waveguide accelerators, produced by femtosecond laser micromachining. A stable plasma waveguide is formed in a hydrogen-filled capillary driven by an all-solid state high-voltage pulser, specially constructed for this purpose. A longitudinal density taper has been confirmed by measurement of the transverse plasma density profiles at both ends of the waveguide and efficient guiding of low intensity (~1012 W/cm2), ultra-short duration (50 fs) laser pulses is demonstrated. For optimal high-power laser conditions (intensity of 1.6 x 1018 W/cm2), electron beams are produced and compared in positively tapered, negatively tapered and straight capillaries with similar plasma densities of 3-6 x 1018 cm-3 over a length of 4 cm. In all three capillaries, low charge (
Author:
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Languages : en
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Author: Joshua Joseph May
Publisher:
ISBN:
Category :
Languages : en
Pages : 250
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The continued development of the chirped pulse amplification technique has allowed for the development of lasers with powers of in excess of $10^{15}W$, for pulse lengths with durations of between .01 and 10 picoseconds, and which can be focused to energy densities greater than 100 giga-atmospheres. When such lasers are focused onto material targets, the possibility of creating particle beams with energy fluxes of comparable parameters arises. Such interactions have a number of theorized applications. For instance, in the Fast Ignition concept for Inertial Confinement Fusion \cite{Tabak:1994vx}, a high-intensity laser efficiently transfers its energy into an electron beam with an appropriate spectra which is then transported into a compressed target and initiate a fusion reaction. Another possible use is the so called Radiation Pressure Acceleration mechanism, in which a high-intensity, circularly polarized laser is used to create a mono-energetic ion beam which could then be used for medical imaging and treatment, among other applications. For this latter application, it is important that the laser energy is transferred to the ions and not to the electrons. However the physics of such high energy-density laser-matter interactions is highly kinetic and non-linear, and presently not fully understood. In this dissertation, we use the Particle-in-Cell code OSIRIS \cite{Fonseca:2002, Hemker:1999} to explore the generation and transport of relativistic particle beams created by high intensity lasers focused onto solid density matter at normal incidence. To explore the generation of relativistic electrons by such interactions, we use primarily one-dimensional (1D) and two-dimensional (2D), and a few three-dimensional simulations (3D). We initially examine the idealized case of normal incidence of relatively short, plane-wave lasers on flat, sharp interfaces. We find that in 1D the results are highly dependent on the initial temperature of the plasma, with significant absorption into relativistic electrons only possible when the temperature is high in the direction parallel to the electric field of the laser. In multi-dimensions, absorption into relativistic electrons arises independent of the initial temperature for both fixed and mobile ions, although the absorption is higher for mobile ions. In most cases however, absorption remains at $10's$ of percent, and as such a standing wave structure from the incoming and reflected wave is setup in front of the plasma surface. The peak momentum of the accelerated electrons is found to be $2 a_0 m_e c$, where $a_0 \equiv e A_0/m_e c^2$ is the normalized vector potential of the laser in vacuum, $e$ is the electron charge, $m_e$ is the electron mass, and $c$ is the speed of light. We consider cases for which $a_0>1$. We therefore call this the $2 a_0$ acceleration process. Using particle tracking, we identify the detailed physics behind the $2 a_0$ process and find it is related to the standing wave structure of the fields. We observe that the particles which gain energy do so by interacting with the laser electric field within a quarter wavelength of the surface where it is at an anti-node (it is a node at the surface). We find that only particles with high initial momentum -- in particular high transverse momentum -- are able to navigate through the laser magnetic field as its magnitude decreases in time each half laser cycle (it is an anti-node at the surface) to penetrate a quarter wavelength into the vacuum where the laser electric field is large. For a circularly polarized laser the magnetic field amplitude never decreases at the surface, instead its direction simply rotates. This prevents electrons from leaving the plasma and they therefore cannot gain energy from the electric field. For pulses with longer durations ($\gtrsim 250fs$), or for plasmas which do not have initially sharp interfaces, we discover that in addition to the $2 a_0$ acceleration at the surface, relativistic particles are also generated in an underdense region in front of the target. These particles have energies without a sharp upper bound. Although accelerating these particles removes energy from the incoming laser, and although the surface of the plasma does not stay perfectly flat and so the standing wave structure becomes modified, we find in most cases, the $2 a_0$ acceleration mechanism occurs similarly at the surface and that it still dominates the overall absorption of the laser. To explore the generation of relativistic electrons at a solid surface and transport of the heat flux of these electrons in cold or warm dense matter, we compare OSIRIS simulations with results from an experiment performed on the OMEGA laser system at the University of Rochester. In that experiment, a thin layer of gold placed on a slab of plastic is illuminated by an intense laser. A greater than order-of-magnitude decrease in the fluence of hot electrons is observed when those electrons are transported through a plasma created from a shock-heated plastic foam, as compared to transport through cold matter (unshocked plastic foam) at somewhat higher density. Our simulations indicate two reasons for the experimental result, both related to the magnetic field. The primary effect is the generation of a collimating B-field around the electron beam in the cold plastic foam, caused by the resistivity of the plastic. We use a Monte Carlo collision algorithm implemented in OSIRIS to model the experiment. The incoming relativistic electrons generate a return current. This generates a resistive electric field which then generates a magnetic field from Faraday's law. This magnetic field collimates the forward moving relativistic electrons. The collisionality of both the plastic and the gold are likely to be greater in the experiment than the 2D simulations where we used a lower density for the gold (to make the simulations possible) which heats up more. In addition, the use of 2D simulations also causes the plastic to heat up more than expected. We compensated for this by increasing the collisionality of the plasma in the simulations and this led to better agreement. The second effect is the growth of a strong, reflecting B-field at the edge of the plastic region in the shock heated material, created by the convective transport of this field back towards the beam source due to the neutralizing return current. Both effects appear to be caused primarily by the difference is density in the two cases. Owing to its higher heat capacity, the higher density material does not heat up as much from the heat flux coming from the gold, which leads to a larger resistivity. Lastly, we explored a numerical effect which has particular relevance to these simulations, due to their high energy and plasma densities. This effect is caused by the use of macro particles (which represent many real particles) which have the correct charge to mass ratio but higher charge. Therefore, any physics of a single charge that scales as $q^2/m$ will be artificially high. Physics that involves scales smaller than the macro-particle size can be mitigated through the use of finite size particles. However, for relativistic particles the spatial scale that matters is the skin depth and the cell sizes and particle sizes are both smaller than this. This allows the wakes created by these particles to be artificially high which causes them to slow down much faster than a single electron. We studied this macro-particle stopping power theoretically and in OSIRIS simulations. We also proposed a solution in which particles are split in to smaller particles as they gain energy. We call this effect Macro Particle Stopping. Although this effect can be mitigated by using more particles, this is not always computationally efficient. We show how it can also be mitigated by using high-order particle shapes, and/or by using a particle-splitting method which reduces the charge of only the most energetic electrons.
Author: Martin Meisel
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Società italiana di fisica
Publisher: IOS Press
ISBN: 1614991294
Category : Science
Languages : en
Pages : 286
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Impressive progress has been made in the field of laser-plasma acceleration in the last decade, with outstanding achievements from both experimental and theoretical viewpoints. Closely exploiting the development of ultra-intense, ultrashort pulse lasers, laser-plasma acceleration has developed rapidly, achieving accelerating gradients of the order of tens of GeV/m, and making the prospect of miniature accelerators a more realistic possibility. This book presents the lectures delivered at the Enrico Fermi International School of Physics and summer school: "Laser-Plasma Acceleration" , held in Varenna, Italy, in June 2011. The school provided an opportunity for young scientists to experience the best from the worlds of laser-plasma and accelerator physics, with intensive training and hands-on opportunities related to key aspects of laser-plasma acceleration. Subjects covered include: the secrets of lasers; the power of numerical simulations; beam dynamics; and the elusive world of laboratory plasmas. The objective of the school was to establish a common knowledge base for the future laser-plasma accelerator community. These published proceedings aim to provide a wider community with a reference covering a wide range of topics, knowledge of which will be necessary to future research on laser-plasma acceleration. The book also provides references to selected existing literature for further reading.
Author: Xinlu Xu
Publisher: Springer Nature
ISBN: 9811523819
Category : Science
Languages : en
Pages : 138
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This book explores several key issues in beam phase space dynamics in plasma-based wakefield accelerators. It reveals the phase space dynamics of ionization-based injection methods by identifying two key phase mixing processes. Subsequently, the book proposes a two-color laser ionization injection scheme for generating high-quality beams, and assesses it using particle-in-cell (PIC) simulations. To eliminate emittance growth when the beam propagates between plasma accelerators and traditional accelerator components, a method using longitudinally tailored plasma structures as phase space matching components is proposed. Based on the aspects above, a preliminary design study on X-ray free-electron lasers driven by plasma accelerators is presented. Lastly, an important type of numerical noise—the numerical Cherenkov instabilities in particle-in-cell codes—is systematically studied.
Author: Alexander Wu Chao
Publisher: World Scientific
ISBN: 981126919X
Category : Science
Languages : en
Pages : 960
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Book Description
Edited by internationally recognized authorities in the field, this expanded and updated new edition of the bestselling Handbook, containing many new articles, is aimed at the design and operation of modern particle accelerators. It is intended as a vade mecum for professional engineers and physicists engaged in these subjects. With a collection of more than 2000 equations, 300 illustrations and 500 graphs and tables, here one will find, in addition to common formulae of previous compilations, hard to find, specialized formulae, recipes and material data pooled from the lifetime experience of many of the world's most able practioners of the art and science of accelerators.The seven chapters include both theoretical and practical matters as well as an extensive glossary of accelerator types. Chapters on beam dynamics and electromagnetic and nuclear interactions deal with linear and nonlinear single particle and collective effects including spin motion, beam-environment, beam-beam, beam-electron, beam-ion and intrabeam interactions. The impedance concept and related calculations are dealt with at length as are the instabilities due to the various interactions mentioned. A chapter on operational considerations including discussions on the assessment and correction of orbit and optics errors, realtime feedbacks, generation of short photon pulses, bunch compression, phase-space exchange, tuning of normal and superconducting linacs, energy recovery linacs, free electron lasers, cryogenic vacuum systems, steady state microbuching, cooling, space-charge compensation, brightness of light sources, collider luminosity optimization and collision schemes, machine learning, multiple frequency rf systems, FEL seeding, ultrafast electron diffraction, and Gamma Factory. Chapters on mechanical and electrical considerations present material data and important aspects of component design including heat transfer and refrigeration. Hardware systems for particle sources, feedback systems, confinement, including undulators, and acceleration (both normal and superconducting) receive detailed treatment in a sub-systems chapter, beam measurement and apparatus being treated therein as well.A detailed name and subject index is provided together with reliable references to the literature where the most detailed information available on all subjects treated can be found.
