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Author: Daniel E. Mittelberger
Publisher:
ISBN:
Category :
Languages : en
Pages : 150
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Book Description
Unlike conventional accelerators, the accelerating structure in a laser plasma accelerator (LPA) is dynamically created by the interaction of a high-peak-power laser pulse with a plasma target. This dynamic nature allows extensive control over the acceleration process but requires detailed knowledge and regulation of the laser, the plasma target, and their interaction. In this thesis, the effect of laser pulse structure, in particular temporal profile and spatiotemporal coupling, on laser plasma acceleration is investigated through theoretical models and experiments at the BErkeley Laboratory Laser Accelerator (BELLA) Center. The temporal profile of the laser and the density profile of the plasma target are probed by laser spectral shifting. A novel model of laser steering and electron beam deflection due to pulse front tilt is developed. The effects of pulse front tilt are measured in experiments and found to be in good agreement with the theoretical model. The application of these results for the optimization of a laser plasma accelerator is discussed.
Author: Daniel E. Mittelberger
Publisher:
ISBN:
Category :
Languages : en
Pages : 150
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Book Description
Unlike conventional accelerators, the accelerating structure in a laser plasma accelerator (LPA) is dynamically created by the interaction of a high-peak-power laser pulse with a plasma target. This dynamic nature allows extensive control over the acceleration process but requires detailed knowledge and regulation of the laser, the plasma target, and their interaction. In this thesis, the effect of laser pulse structure, in particular temporal profile and spatiotemporal coupling, on laser plasma acceleration is investigated through theoretical models and experiments at the BErkeley Laboratory Laser Accelerator (BELLA) Center. The temporal profile of the laser and the density profile of the plasma target are probed by laser spectral shifting. A novel model of laser steering and electron beam deflection due to pulse front tilt is developed. The effects of pulse front tilt are measured in experiments and found to be in good agreement with the theoretical model. The application of these results for the optimization of a laser plasma accelerator is discussed.
Author: Philip K. Franke
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
"Laser produced plasma provides a basis for many emerging technologies because it can interact with photons and charged particles in powerful and unique ways. These laser-plasma-based applications frequently rely on the controlled coupling of the laser pulse to the plasma to achieve the desired effects. Spatiotemporal (ST) pulse shaping, referring to the intentional correlation of the spatial and temporal characteristics of the laser pulse, can enhance control over the laser-plasma coupling improving the utility of laser-plasma-based applications. This work presents the basic theory of two ST shaping techniques, the chromatic flying focus (CFF) [D.H. Froula et al., "Spatiotemporal control of laser intensity" Nature Photonics 12, 262?265 (2018), D.H. Froula et al., "Flying focus: Spatial and temporal control of intensity for laser-based applications" Physics of Plasmas 26] and the ultrashort flying focus (UFF) ["Dephasingless Laser Wakefield Acceleration" Physical Review Letters 124, 134802 (2020)], and explores their applications experimentally and theoretically. Both techniques have at least three advantages in common: 1) laser pulse focusing is cylindrically symmetric, allowing high focused intensities to be reached, 2) the focal range is decoupled from the spot size, allowing high intensity to be maintained over long distances, and 3) the intensity peak velocity (focal velocity, v f) is decoupled from the laser group velocity, facilitating intensity peaks with tunable velocity. CFF pulses derived from the Multi-Terawatt laser at the Laboratory for Laser Energetics were used to drive ionization waves of arbitrary velocity (IWAVs) in air. These IWAVs, which are the moving interface between a neutral medium and an ionized plasma, moved at the focal velocity v f when driven by low energy pulses with uniform power spectra, agreeing with theoretical predictions. Focal velocity ranges shown computationally to mitigate ionization refraction were also confirmed [D. Turnbull et al., "Ionization Waves of Arbitrary Velocity" Physical Review Letters 120, 225001 (2018), J.P. Palastro et al., "Ionization waves of arbitrary velocity driven by a flying focus" Physical Review A 97, 033835 (2018)]. Later experiments demonstrated IWAVs of large diameter using defocused laser pulses in a gas jet. The non-uniform power spectrum of these higher energy pulses resulted in experimentally observable changes to the IWAV diameter and trajectory. An analytic theory predicting the IWAV trajectory and diameter for CFF pulses with non-uniform power spectra was developed, and broadly agreed with the experimental observations. This theory was used to propose the use of power spectrum shaping as a way to better tune the IWAV characteristics [P. Franke et al., "Measurement and control of large diameter ionization waves of arbitrary velocity" Optics Express 27, 31978?31988 (2019)]. Photon acceleration, describing the continual frequency increase accrued by a photon in a time decreasing refractive index gradient as a means to generate extreme ultraviolet light, is an application shown computationally to be advanced by the generation of IWAVs. A computational investigation of three photon acceleration schemes enable by IWAVs is presented. A new optical shock-enhanced self-photon acceleration regime was identified using a finite-difference time-domain computational model. This regime, which is characterized by rapid spectral broadening and temporal compression of the drive laser pulse, could generate isolated attosecond pulses in the extreme ultraviolet with high efficiency [A.J. Howard et al., "Photon Acceleration in a Flying Focus" Physical Review Letters 123, 124801 (2019), P. Franke et al., "Optical shock-enhanced self-photon acceleration" Physical Review A 104, 043520 (2021)]. An experimental platform was developed to measure the UFF, and prototype radial echelon optics were manufactured. The echelon optics were fabricated using vapor-deposition through a rotating mask, and were measured to be suitable for initial experiments. An automated scanning spectral interferometer was built and benchmarked, then used to make initial measurements of the UFF. The UFF was not explicitly demonstrated, but several experimental shortcomings were identified, illuminating a path toward an ultimate demonstration. A successful demonstration of the UFF will immediately enable a series of experiments planned to study dephasingless laser wakefield acceleration and related topics"--Pages xi-xiii
Author:
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Category :
Languages : en
Pages :
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Decoupling injection from acceleration is a key challenge to achieve compact, reliable, tunable laser-plasma accelerators (LPA). In colliding pulse injection the beat between multiple laser pulses can be used to control energy, energy spread, and emittance of the electron beam by injecting electrons in momentum and phase into the accelerating phase of the wake trailing the driver laser pulse. At LBNL, using automated control of spatiotemporal overlap of laser pulses, two-pulse experiments showed stable operation and reproducibility over hours of operation. Arrival time of the colliding beam was scanned, and the measured timing window and density of optimal operation agree with simulations. The accelerator length was mapped by scanning the collision point.
Author: Satomi Shiraishi
Publisher: Springer
ISBN: 3319085697
Category : Science
Languages : en
Pages : 133
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Book Description
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: Brian Henry Shaw
Publisher:
ISBN:
Category :
Languages : en
Pages : 111
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Book Description
For over 10 years, laser plasma acceleration (LPA) has been a rapidly growing technology used to create electron beams on length-scales much smaller than that of a conventional RF-accelerator [1]. As electron beam properties improve, research for LPAs is expanding to take advantage of the creation and accessibility of high-quality electron beams from plasma targets. Two applications which are currently being explored are a multi-stage plasma accelerator to reach energies greater than those a single-stage accelerator can achieve and exploring the possibility of an LPA based free-electron laser (FEL) light source. Research supporting both of these efforts has been performed on the 50 TW TREX laser system at the BELLA Center at the Lawrence Berkeley National Lab, and the results of these efforts are described in this dissertation. Using chirped-pulsed amplification to produce high-quality laser pulses up to petawatt levels, experimental results have yielded laser driven electron beam energies up to 4.25 GeV [2]. By tuning the density of the target, the accelerating gradients sustained by the plasma can grow beyond 100 GeV/m [3] (10^3 times larger than that of a conventional RF accelerator). However, limiting factors such as dephasing of the electron beam from the plasma wake, defocusing of a laser pulse, and energy depletion of the laser into the plasma limit the maximum sensible length of a plasma accelerator. Staging the LPA with two or more accelerating modules could be the next step towards producing beams with energies greater than those possible with a single stage. One requirement for staged acceleration is that the laser pulse used to drive the first accelerating stage must be coupled out of the beamline, and a fresh laser pulse must be coupled in for the second stage to post accelerate the electrons. To do this while maintaining a short scale length between the two stages requires an optic to be placed near the final focus of the second laser pulse. Because damage will occur when the laser pulse interacts with a steering optic near focus, the coupling optic must be capable of replacing the surface following damage on each successive shot. This thesis comprises a detailed investigation of the physics of using a plasma mirror (PM) from a tape by reflecting ultrashort pulses from a laser-triggered surface plasma. The tapes used in the characterization of the PM are VHS and computer data storage tape. The tapes are 6.6 m (computer storage tape) and 15 m (VHS) thick. Each tape is 0.5 inches wide, and 10s of meters of tape are spooled using a tape drive; providing thousands of shots on a single reel of tape. The amount of reflected energy of the PM was studied for different input intensities. The fluence was varied by translating the focus of the laser upstream and downstream of the tape, which changed the spot size on the tape surface and hence changed the fluence. This study measured reflectances from both sides of the two tapes, and for input light of both s and p-polarizations. Lastly, an analytic model was developed to understand the reflectance as a function of fluence for each tape material and polarization. Another application that benefits from the advancements of LPA technology is an LPAbased FEL. By sending a high quality electron bunch through an undulator (a periodic structure of positive and negative magnetic poles), the electrons oscillate transversely to the propagation axis and produce radiation. The 1.5 m THUNDER undulator [4] at the BELLA Center has been commissioned using electron beams of 400MeV beams with broad energy spread (35%) [5]. To produce a coherent LPA-based FEL, the beam quality would need to improve to sub-percent level energy spread. A seed source could be used to help induce bunching of the electron beam within the undulator. This thesis described the experimental investigation of the physics of using solid-based surface high-harmonic generation (SHHG) from a thin tape as a possible seed source for an FEL. A thin tape placed within centimeters of the undulator's entrance could act as a harmonic generating source, while simultaneously transmitting an electron beam. This removes the need for transport optics for the XUV photons and the need for additional optics to overlap the seed beam with the electron beam at the undulator entrance. By operating at sub-relativistic laser strengths, harmonics up to the 17th order of 800 nm light are produced using an SHHG technique known as coherent wake emission (CWE). CWE pulse properties such as divergence, energy, conversion efficiency, and spectrum are measured for a wide range of tape materials and drive laser conditions. A clear correlation between surface roughness and harmonic beam divergence is found. The measured pulse properties for the 15th harmonic from VHS tape (conversion efficiency 6.5x10^-7 and an rms divergence of 12 mrad), the 100 mJ-level, 40-50 fs-class drive laser, produces peak powers of several MW's of XUV pulses. The results of a 1D model indicate that these CWE pulses with MW level powers are sufficient for seed-induced FEL gain.
Author:
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ISBN:
Category :
Languages : en
Pages : 181
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This dissertation documents the development of a broadband electron spectrometer (ESM) for GeV class Laser Wakefield Accelerators (LWFA), the production of high quality GeV electron beams (e-beams) for the first time in a LWFA by using a capillary discharge guide (CDG), and a statistical analysis of CDG-LWFAs. An ESM specialized for CDG-LWFAs with an unprecedented wide momentum acceptance, from 0.01 to 1.1 GeV in a single shot, has been developed. Simultaneous measurement of e-beam spectra and output laser properties as well as a large angular acceptance (> ± 10 mrad) were realized by employing a slitless scheme. A scintillating screen (LANEX Fast back, LANEX-FB)--camera system allowed faster than 1 Hz operation and evaluation of the spatial properties of e-beams. The design provided sufficient resolution for the whole range of the ESM (below 5% for beams with 2 mrad divergence). The calibration between light yield from LANEX-FB and total charge, and a study on the electron energy dependence (0.071 to 1.23 GeV) of LANEX-FB were performed at the Advanced light source (ALS), Lawrence Berkeley National Laboratory (LBNL). Using this calibration data, the developed ESM provided a charge measurement as well. The production of high quality electron beams up to 1 GeV from a centimeter-scale accelerator was demonstrated. The experiment used a 310 ?m diameter gas-filled capillary discharge waveguide that channeled relativistically-intense laser pulses (42 TW, 4.5 x 1018 W/cm2) over 3.3 centimeters of sufficiently low density (≃ 4.3 x 1018/cm3) plasma. Also demonstrated was stable self-injection and acceleration at a beam energy of ≃ 0.5 GeV by using a 225 ?m diameter capillary. Relativistically-intense laser pulses (12 TW, 1.3 x 1018W/cm2) were guided over 3.3 centimeters of low density (≃ 3.5 x 1018/cm3) plasma in this experiment. A statistical analysis of the CDG-LWFAs performance was carried out. By taking advantage of the high repetition rate experimental system, several thousands of shots were taken in a broad range of the laser and plasma parameters. An analysis program was developed to sort and select the data by specified parameters, and then to evaluate performance statistically. The analysis suggested that the generation of GeV-level beams comes from a highly unstable and regime. By having the plasma density slightly above the threshold density for self injection, (1) the longest dephasing length possible was provided, which led to the generation of high energy e-beams, and (2) the number of electrons injected into the wakefield was kept small, which led to the generation of high quality (low energy spread) e-beams by minimizing the beam loading effect on the wake. The analysis of the stable half-GeV beam regime showed the requirements for stable self injection and acceleration. A small change of discharge delay tdsc, and input energy Ein, significantly affected performance. The statistical analysis provided information for future optimization, and suggested possible schemes for improvement of the stability and higher quality beam generation. A CDG-LWFA is envisioned as a construction block for the next generation accelerator, enabling significant cost and size reductions.
Author: Dino A. Jaroszynski
Publisher: CRC Press
ISBN: 1584887796
Category : Science
Languages : en
Pages : 454
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Book Description
A Solid Compendium of Advanced Diagnostic and Simulation ToolsExploring the most exciting and topical areas in this field, Laser-Plasma Interactions focuses on the interaction of intense laser radiation with plasma. After discussing the basic theory of the interaction of intense electromagnetic radiation fields with matter, the book covers three ap
Author: National Academies of Sciences Engineering and Medicine
Publisher:
ISBN: 9780309677608
Category :
Languages : en
Pages : 291
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Book Description
Plasma Science and Engineering transforms fundamental scientific research into powerful societal applications, from materials processing and healthcare to forecasting space weather. Plasma Science: Enabling Technology, Sustainability, Security and Exploration discusses the importance of plasma research, identifies important grand challenges for the next decade, and makes recommendations on funding and workforce. This publication will help federal agencies, policymakers, and academic leadership understand the importance of plasma research and make informed decisions about plasma science funding, workforce, and research directions.
Author: Paul Gibbon
Publisher: World Scientific
ISBN: 1911298844
Category : Science
Languages : en
Pages : 328
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Book Description
This book represents the first comprehensive treatment of the subject, covering the theoretical principles, present experimental status and important applications of short-pulse laser-matter interactions.Femtosecond lasers have undergone dramatic technological advances over the last fifteen years, generating a whole host of new research activities under the theme of “ultrafast science”. The focused light from these devices is so intense that ordinary matter is torn apart within a few laser cycles. This book takes a close-up look at the exotic physical phenomena which arise as a result of this new form of “light-matter” interaction, covering a diverse set of topics including multiphoton ionization, rapid heatwaves, fast particle generation and relativistic self-channeling. These processes are central to a number of exciting new applications in other fields, such as microholography, optical particle accelerators and photonuclear physics.Repository for numerical models described in Chapter 6 can be found at www.fz-juelich.de/zam/cams/plasma/SPLIM/./a
Author: Jean-Claude Diels
Publisher: Elsevier
ISBN: 0080466400
Category : Science
Languages : en
Pages : 675
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Book Description
Ultrashort Laser Pulse Phenomena, Second Edition serves as an introduction to the phenomena of ultra short laser pulses and describes how this technology can be used to examine problems in areas such as electromagnetism, optics, and quantum mechanics. Ultrashort Laser Pulse Phenomena combines theoretical backgrounds and experimental techniques and will serve as a manual on designing and constructing femtosecond ("faster than electronics") systems or experiments from scratch. Beyond the simple optical system, the various sources of ultrashort pulses are presented, again with emphasis on the basic concepts and how they apply to the design of particular sources (dye lasers, solid state lasers, semiconductor lasers, fiber lasers, and sources based on frequency conversion). - Provides an easy to follow guide through "faster than electronics" probing and detection methods - THE manual on designing and constructing femtosecond systems and experiments - Discusses essential technology for applications in micro-machining, femtochemistry, and medical imaging
