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1
Bajlekov, Svetoslav. "Towards a free-electron laser driven by electrons from a laser-wakefield accelerator : simulations and bunch diagnostics." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:99f9f13a-d0c2-4dd8-a9a4-13926621c352.
Повний текст джерелаАнотація:
This thesis presents results from two strands of work towards realizing a free-electron laser (FEL) driven by electron bunches generated by a laser-wakefield accelerator (LWFA). The first strand focuses on selecting operating parameters for such a light source, on the basis of currently achievable bunch parameters as well as near-term projections. The viability of LWFA-driven incoherent undulator sources producing nanojoule-level pulses of femtosecond duration at wavelengths of 5 nm and 0.5 nm is demonstrated. A study on the prospective operation of an FEL at 32 nm is carried out, on the basis of scaling laws and full 3-D time-dependent simulations. A working point is selected, based on realistic bunch parameters. At that working point saturation is expected to occur within a length of 1.6 m with peak power at the 0.1 GW-level. This level, as well as the stability of the amplification process, can be improved significantly by seeding the FEL with an external radiation source. In the context of FEL seeding, we study the ability of conventional simulation codes to correctly handle seeds from high-harmonic generation (HHG) sources, which have a broad bandwidth and temporal structure on the attosecond scale. Namely, they violate the slowly-varying envelope approximation (SVEA) that underpins the governing equations in conventional codes. For this purpose we develop a 1-D simulation code that works outside the SVEA. We carry out a set of benchmarks that lead us to conclude that conventional codes are adequately capable of simulating seeding with broadband radiation, which is in line with an analytical treatment of the interaction. The second strand of work is experimental, and focuses on on the use of coherent transition radiation (CTR) as an electron bunch diagnostic. The thesis presents results from two experimental campaigns at the MPI für Quantenoptik in Garching, Germany. We present the first set of single-shot measurements of CTR over a continuous wavelength range from 420 nm to 7 μm. Data over such a broad spectral range allows for the first reconstruction of the longitudinal profiles of electron bunches from a laser-wakefield accelerator, indicating full-width at half-maximum bunch lengths around 1.4 μm (4.7 fs), corresponding to peak currents of several kiloampères. The bunch profiles are reconstructed through the application of phase reconstruction algorithms that were initially developed for studying x-ray diffraction data, and are adapted here for the first time to the analysis of CTR data. The measurements allow for an analysis of acceleration dynamics, and suggest that upon depletion of the driving laser the accelerated bunch can itself drive a wake in which electrons are injected. High levels of coherence at optical wavelengths indicate the presence of an interaction between the bunch and the driving laser pulse.
2
Restivo, Rick A. "Free electron laser weapons and electron beam transport." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA333358.
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3
Stetler, Aaron M. "Active vibration control for free electron lasers." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FStetler.pdf.
Повний текст джерелаАнотація:
Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2003.Thesis advisor(s): Bruce C. Denardo, Thomas J. Hofler. Includes bibliographical references (p. 81). Also available online.
4
Dearden, Geoffrey. "An industrial free electron laser." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240478.
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5
Petichakis, Christos. "The Cerenkov free electron laser." Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399079.
Повний текст джерелаАнотація:
This thesis reports on an investigation into Cerenkov Free Electron Lasers. These devices are basically travelling wave tubes but having a dielectrically lined cylinder as the slow wave structure rather than a helix. If an electron beam is injected into the centre of this structure, an interaction between the electrons and the electromagnetic (e-m) TMo I mode can occur which can lead to amplification of the e-m wave. Two different systems have been constructed. The first one was designed to operate as an oscillator at 12.4GHz and used a rectangular X-band waveguide microwave coupler. It was thought that the non-operation of this device could have been due to a lack of net gain, and so a second system was designed having a smaller diameter dielectric liner in order to achieve higher gain but at a slightly higher frequency of operation (l6.9GHz). In both systems, the interception of the electron beam with the dielectric liner was small. Unfortunately, even though a maximum electron beam current of 120mA was achieved, leading to an expected small signal gain of 1200%, no microwave output was observed either. At this stage it was considered that there must he something more fundamental at fault with these systems. After a thorough investigation. it was discovered that the small gap which always exists between the dielectric liner and the waveguide affected the dispersion relation of a Cerenkov system. Theoretically, gaps as small as 1 % of the diameter of the waveguide were found to have a serious effect, and although these gaps would not stop the operation of the Cerenkov device, microwave output would only be expected at a voltage far from that expected. It was found that the problem could be overcome by coating the outer surface of the dielectric tube with a layer of conducting material, such as silver paint, which effectively removes the gap. Further tests of a Cerenkov free electron laser with this improvement are in progress.
6
Evtushenko, Pavel. "Electron beam diagnostic at the ELBE free electron laser." Doctoral thesis, [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972779876.
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Evtushenko, P. "Electron Beam Diagnostic at the ELBE Free Electron Laser." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28802.
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Evtushenko, P. "Electron Beam Diagnostic at the ELBE Free Electron Laser." Forschungszentrum Rossendorf, 2004. https://hzdr.qucosa.de/id/qucosa%3A21707.
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Mitchell, Ethan D. "Multiple beam directors for naval free electron laser weapons." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FMitchell.pdf.
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Massey, Daniel S. "Simulation of DARMSTADT Free Electron Laser and a comparison of high gain Free Electron Laser." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA387394.
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11
You, Yan. "Pulsed Laser Injected Enhancement Cavity for Laser-electron Interaction." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01011958.
Повний текст джерелаАнотація:
X-ray diffraction and scattering, X-ray spectroscopy, and X-ray crystallography are widely used in the life sciences, material science, and medical diagnosis. High-quality and high-brightness X-rays are a strong requirement to improve applications. Inverse Compton scattering (ICS) X-ray source has attracted great interests worldwide lately. To significantly enhance the average X-ray photon flux, a compact electron storage-ring combined with a high finesse optical enhancement cavity (OEC) can be utilized. In such a system, the collision rate between the electron beam and the laser pulse is greatly increased to the MHz range, enabling a photon flux up to 10¹³ph/s.In the first chapter, I describe the motivation behind the development of OEC based on ICS X-ray source. The characteristics of this kind of X-ray source are summarized, compared to those of the conventional low-repetition-rate Terawatt laser system based on ICS X-ray source. The latest progress and research status of OEC based on ICS X-ray source are presented. Pulsed-laser injected high-finesse OEC stacking theory and properties are discussed in Chapter 2. Not only does the OEC based on ICS X-ray source require the laser pulse repetition rate to be matched to the free spectral range (FSR) of the cavity, where both also have to match the electron storage-ring circulation frequency. In addition, we have to match the phase shift of the laser repetition rate to the phase offset introduced by the dispersion of the cavity mirrors, since our cavity finesse design value is quite high. The stacking theory is analyzed in the frequency domain. Cavity properties, including cavity mirror dispersion, finesse, and FSR, are discussed in detail. A laser frequency comb and OEC coupling is analyzed also. The laser source development is presented in Chapter 3. We constructed a mode-locked fiber laser based on nonlinear polarization rotation. The locking model, locking techniques, and the theory, simulations and experimental tests of tilt locking (TL) in the pulsed laser injected high-finesse OEC are discussed in Chapter 4. We succeeded in locking a pulsed laser to a high-finesse cavity with the TL technique. The experimental results show that the TL and the Pound-Drever-Hall techniques have the same performance: stable locking, high sensitivity, and the same power coupling rate for picosecond laser pulse case, while the test results for full spectrum TL locking show that it is uneasy to align the split-photodiode to the beam waist.Based on the above experimental study and tests, we design the OEC system for Tsinghua University X-ray project in Chapter 5. The expected X-ray flux is 10¹º to 10¹³ ph/s. We detail every subsystem requirement.
12
Williams, Robert E. "Naval electric weapons : the electromagnetic railgun and free electron laser /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FWilliams.pdf.
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Ghaith, Amin. "Towards compact and advanced Free Electron Laser." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS333/document.
Повний текст джерелаАнотація:
Les lasers à électrons libres (LEL) X sont aujourd'hui des sources lumineuses cohérentes et intenses utilisées pour des investigations multidisciplinaires de la matière. Un nouveau schéma d'accélération, l'accélérateur laser plasma (LPA), est maintenant capable de produire une accélération de quelques GeV/cm, bien supérieure à celle des linacs radiofréquence. Ce travail de thèse a été mené dans le cadre des programmes de R&D du projet LUNEX5 (laser à électrons libres utilisant un nouvel accélérateur pour l’exploitation du rayonnement X de 5e génération) de démonstrateur LEL avancé et compact avec applications utilisatrices pilotes. Il comprend un linac supraconducteur de 400 MeV de haute cadence (10 kHz) pour l’étude de schémas LEL avancés, et LPA pour sa qualification par une application LEL. La ligne LEL utilise une configuration d’injection avancée dans la plage spectrale 40-4 nm par génération d’harmoniques à gain élevé (HGHG) et schéma d’écho (EEHG) avec des onduleurs compacts cryogéniques à champ élevé de courte période courte. L'étude de solutions adaptées aux applications LEL compactes et avancées est donc examinée. Un premier aspect concerne la réduction du milieu de gain du LEL (électrons dans l'onduleur), le raccourcissement de la période se faisant au détriment du champ magnétique. Les onduleurs cryogéniques compacts à base d'aimants permanents cryogéniques (CPMU), dans lesquels les performances de l'aimant sont améliorées à la température cryogénique sont étudiés. Une deuxième partie du travail développée dans le cadre l’expérience de R&D COXINEL visant à démontrer l’amplification LEL à l’aide d’un LPA. La ligne permet de manipuler les propriétés des faisceaux d’électrons produits (dispersion en énergie, divergence, variation de pointé) avant d’être utilisées pour des applications de sources lumineuses. Le faisceau d'électrons généré est très divergent et nécessite une bonne manipulation juste après la source avec des quadrupôles forts placés immédiatement après la génération d'électrons. Ainsi, des quadrupôles innovants à aimants permanents de gradient élevé réglable appelés «QUAPEVA», sont développés. Ils sont optimisés avec le code RADIA et caractérisées avec trois mesures magnétiques. Un gradient de 200 T/m avec une variabilité de 50 % est obtenu tout en maintenant une excursion du centre magnétique réduite à ± 10 µm, qui a permis un alignement par compensation de pointé du faisceau dans COXINEL grâce au centre magnétique variable des systèmes, avec un faisceau bien focalisé sans dispersion. Les QUAPEVA constituent des systèmes originaux dans le paysage des quadrupôles à de gradient élevé et variable développés jusqu'à présent. Une troisième partie des travaux concerne l’observation du rayonnement d’onduleur monochromatique ajustable sur la ligne COXINEL. Le faisceau d'électrons d'énergie de 170 MeV est transporté et focalisé dans un CPMU de 2 m et de période de 18 mm émettant à 200 nm. Le flux spectral est caractérisé à l'aide d'un spectromètre UV et le flux angulaire mesuré par une caméra CCD. La longueur d'onde est accordée avec l’entrefer. Les distributions spatio-spectrales mesurées en forme de lune du rayonnement de l'onduleur sont bien reproduites par les simulations de rayonnement utilisant les distributions d’électrons mesurées et transportées le long de la ligne. Elles permettent aussi de renseigner sur la qualité du faisceau d’électrons, de son transport et d'en estimer les paramètres tels que la dispersion en énergie et la divergence. Le dernier aspect du travail est lié à la comparaison entre la génération des harmoniques en gain élevé et le schéma d’écho, dans le cadre de ma participation à une expérience réalisée à FERMI @ ELETTRA. Nous avons pu démontrer un LEL de type écho à 5,9 nm, avec spectres plus étroits et une meilleure reproductibilité que le schéma HGHG à deux étages. Cette thèse constitue un pas en avant vers les lasers à électrons libres compacts et avancésX-ray Free Electron Lasers (FEL) are nowadays unique intense coherent fs light sources used for multi-disciplinary investigations of matter. A new acceleration scheme such as Laser Plasma Accelerator (LPA) is now capable of producing an accelerating gradient of few GeV/cm far superior to that of conventional RF linacs. This PhD work has been conducted in the framework of R&D programs of the LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) project of advanced and compact Free Electron laser demonstrator with pilot user applications. It comprises a 400 MeV superconducting linac for studies of advanced FEL schemes, high repetition rate operation (10 kHz), multi-FEL lines, a Laser Wake Field Accelerator (LWFA) for its qualification by a FEL application. The FEL lines comports enables advanced seeding in the 40-4 nm spectral range using high gain harmonic generation (HGHG) and echo-enabled harmonic generation (EEHG) with compact short period high field cryogenic undulators. The study of compact devices suitable for compact FEL applications is thus examined. One first aspect concerns the reduction of the Free Electron Laser gain medium (electrons in undulator) where shortening of the period is on the expense of the magnetic field leading to an intensity reduction at high harmonics. Compact cryogenic permanent magnet based undulators (CPMUs), where the magnet performance is increased at cryogenic temperature making them suitable for compact applications, are studied. Three CPMUs of period 18 mm have been built: two are installed at SOLEIL storage ring and one at COXINEL experiment. A second part of the work is developed in the frame of the R&D programs is the COXINEL experiment with an aim at demonstrating FEL amplification using an LPA source. The line enables to manipulate the properties of the produced electron beams (as energy spread, divergence, induced dispersion due) before being used for light source applications. The electron beam generated is highly divergent and requires a good handling at an early stage with strong quadrupoles, to be installed immediately after the electron generation source. Hence, the development of the so-called QUAPEVAs, innovative permanent magnet quadrupoles with high tunable gradient, is presented. The QUAPEVAs are optimized with RADIA code and characterized with three magnetic measurements. High tunable gradient is achieved while maintaining a rather good magnetic center excursion that allowed for beam pointing alignment compensation at COXINEL, where the beam is well-focused with zero dispersion at any location along the line. The QUAPEVAs constitute original systems in the landscape of variable high gradient quadrupoles developed so far. A third part of the work concerns the observation of tunable monochromatic undulator radiation on the COXINEL line. The electron beam of energy of 170 MeV is transported and focused in a 2-m long CPMU with a period of 18 mm emitting radiation light at 200 nm. The spectral flux is characterized using a UV spectrometer and the angular flux is captured by a CCD camera. The wavelength is tuned with the undulator gap variation. The spatio-spectral moon shape type pattern of the undulator radiation provided an insight on the electron beam quality and its transport enabling the estimation of the electron beam parameters such as energy spread and divergence. The final aspect of the work is related to the comparison between the echo and high gain harmonic generation, in the frame of my participation to an experiment carried out at FERMI@ELETTRA. At FERMI, we have demonstrated a high gain lasing using EEHG at a wavelength of 5.9 nm where it showed a narrower spectra and better reproducibility compared to a two-stage HGHG. This PhD work constitutes a step forward towards advanced compact Free Electron Lasers
14
Yan, Xiaoling. "Ultra-fast photon and electron beam diagnostics for free electron lasers." Thesis, Abertay University, 2003. https://rke.abertay.ac.uk/en/studentTheses/4a05ee9c-2ddb-434f-b2a1-0ad483394db8.
Повний текст джерелаАнотація:
Characterisation of the ultra-short optical pulses produced by infrared ffee-electron lasers (FELs) is an important task, not only for the further development of free electron lasers and their theory, but also for their operation as a research tool. The setting up and optimisation of the FEL requires effective and reliable diagnostics tools. This thesis presents techniques for the measurement of sub-picosecond optical and electron pulses. A range of techniques is developed that allows measurements of the electric field of both optical pulses and electron bunches to be made with an accuracy of better than 100 fs. These techniques have been used to obtain the first complete electricfield characterisation of ultra-short pulses from a far-infrared FEL; to study the formation of singlesided exponential optical pulses in two FELs; and to obtain the longitudinal profile of electron bunches, both by probing the near-field transition radiation and by directly sensing the Coulomb field of the electron bunches. Although the techniques described are not truly single-shot - requiring measurements averaged over a period of a few microseconds - ways in which they could be extended to provide single-shot capability are discussed.
15
MacKay, John Stuart. "The United Kingdom free electron laser." Thesis, Heriot-Watt University, 1987. http://hdl.handle.net/10399/1049.
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Quirk, Eamonn George. "A 'pre-bunched' free electron laser." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284151.
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Xu, Junliang. "Ultrafast imaging: laser induced electron diffraction." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/13616.
Повний текст джерелаАнотація:
Doctor of PhilosophyDepartment of Physics
Chii-Dong Lin
Imaging of molecules has always occupied an essential role in physical, chemical and biological sciences. X-ray and electron diffraction methods routinely achieve sub-angstrom spatial resolutions but are limited to probing dynamical timescales longer than a picosecond. With the advent of femtosecond intense lasers, a new imaging paradigm emerges in last decade based on laser-induced electron diffraction (LIED). It has been placed on a firm foundation by the quantitative rescattering theory, which established that large-angle e-ion elastic differential cross sections (DCS) can be retrieved from the LIED spectrum. We further demonstrate that atomic potentials can be accurately retrieved from those extracted DCSs at energies from a few to several tens of electron volts. Extending to molecules, we show mid-infrared (mid-IR) lasers are crucial to generate high-energy electron wavepackets (> 100 eV) to resolve the atomic positions in a molecule. These laser-driven 100 eV electrons can incur core-penetrating collisions where the momentum transfer is comparable to those attained in conventional keV electron diffraction. Thus a simple independent atom model (IAM), which has been widely used in conventional electron diffractions, may apply for LIED. We theoretically examine and validate the applicability of IAM for electron energies above 100 eV using e-molecule large-angle collision data obtained in conventional experiments, demonstrating its resolving powers for bond lengths about 0.05 angstrom. The Validity of IAM is also checked by an experimental LIED investigation of rare gas atoms in the mid-IR regime. We show that the electron’s high energy promotes core-penetrating collisions at large scattering angles, where the e-atom interaction is dominated by the strong short range atomic-like potential. Finally, we analyze the measured LIED spectrum of N[subscript]2 and O[subscript]2 at three mid-IR wavelengths (1.7, 2.0, and 2.3 μm). As expected, the retrieved bond lengths of N[subscript]2 at three wavelengths are about same as the equilibrium N[subscript]2 bond length. For O[subscript]2, the data is also consistent with a bond length contraction of 0.1 angstrom within 4-6 fs after tunnel ionization. This investigation establishes a foundation for this novel imaging method for spatiotemporal imaging of gas-phase molecules at the atomic scale.
18
Wenthaus, Lukas [Verfasser]. "Laser-Assisted Photoemission from Solids with Free Electron Lasers / Lukas Wenthaus." München : Verlag Dr. Hut, 2018. http://d-nb.info/1170473407/34.
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19
Hyldgaard, Per. "Noneqilibrium Electron-Electron Scattering in Possible Far-Infrared Quantum Cascade Laser." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392908012.
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Hyldgaard, Per. "Nonequilibrium electron-electron scattering in possible far-infrared quantum cascade laser /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487929745336983.
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Anania, Maria Pia. "Towards a free-electron laser driven by a laser wakefield accelerator." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25451.
Повний текст джерелаАнотація:
The free-electron laser (FEL) is a powerful source of tuneable coherent radiation that currently demands kilometre-scale beam lines for high-energy vacuum ultraviolet (VUV) and X-ray output. Driving an FEL with a laser wakefield accelerator (LWFA) electron beam would radically reduce the size of such systems as well as delivering ultra-short duration radiation pulses. In this thesis, the production and optimal transport of high-quality electron beams in an LWFA and the feasibility of using such beams to drive a VUV FEL has been investigated. The ALPHA-X LWFA uses a 25 TW femtosecond laser pulse focused into a 2 mm gas jet to accelerate electrons. Using simulation codes [General Particle Tracer (GPT) and TRANSPORT], the initial ALPHA-X transport system has been analysed and an improved system using additional permanent magnet quadrupoles has been designed and installed. GPT has also been applied in analysis of the beam transport through a high resolution magnetic dipole electron spectrometer. It is shown that measurements of beam energy spreads of less than 1% imply a normalised transverse emittance of less than 1µ mm mrad, showing that these beams are suitable for driving an FEL. Efficient electron beam transport through an undulator (100 periods, period = 15 mm) is demonstrated implying an estimated source diameter of 300 µ close to the centre of the undulator (in agreement with simulation). Undulator radiation have been generated using electron beams of energy 83-131 MeV. Output radiation spans the range 180-500 nm and the scaling of photon yield with electron charge provides tentative evidence of coherent emission - the radiation flux is up to ~3 times greater than the expected spontaneous emission flux. The maximum number of photons peaks at 8 x 10p⁶ and, assuming a pulse duration of 100 fs, the maximum peak brilliance is 10¹⁸ photons/second/mm²/mrad²/0.1% bandwidth.
22
Lehe, Rémi. "Improvement of laser-wakefield accelerators: towards a compact free electron laser." Palaiseau, Ecole polytechnique, 2014. https://tel.archives-ouvertes.fr/tel-01088398/document.
Повний текст джерелаАнотація:
Lorsque l'on focalise une impulsion laser courte et intense dans un gazsous-dense, celle-ci peut accélérer une fraction des électrons du gaz,et ainsi générer un faisceau d'électrons ayant une énergie de quelquescentaines de MeV. Ce phénomène, connu sous le nom d'accélérationlaser-plasma, pourrait avoir de nombreuses applications,notamment pour la réalisation de sources de rayons Xultra-intenses appelées lasers à électrons libres (LEL). Cependant,ces applications nécessitent que le faisceau d'électrons ait uneexcellente qualité (faible divergence, faible émittance et faible dispersion en énergie). Au cours de cette thèse, différentes solutions ont été développéesafin d'améliorer la qualité des faisceaux d'électrons issus del'accélération laser-plasma. Ce travail est effectué à travers desmodèles analytiques ainsi que dessimulations Particle-In-Cell (PIC). Nous commençons cependant par montrer que les simulations PIC onttendance à surestimer l'émittance du faisceau, en raison de l'effetCherenkov numérique. Afin d'estimer correctement l'émittance ici, nousproposons un algorithme PIC modifié qui n'est pas sujet à l'effetCherenkov numérique. A l'aide de cet algorithme, un nouveau mécanisme permettant de générerle faisceau est observé puis étudié : il s'agit de l'injection optique transverse. Les faisceaux produits par ce mécanisme sontcaractérisés par une forte charge, une faible divergence et une faibleémittance. Par ailleurs, nous proposons un dispositif - la lentille laser-plasma - qui permet defortement réduire la divergence finale des faisceaux. Cesrésultats sont placés dans leur contexte, à travers une discussion despropriétés nécessaires pour un laser à électrons libres compact. Nousmontrons en particulier que les accélérateurs laser-plasma pourraientêtre avantageusement combinés avec des onduleurs laser-plasmainnovants, afin de produire des sources de rayons X intensesWhen an intense and short laser pulse propagates through an underdensegas, it can accelerate a fraction of the electrons of the gas, andthereby generate an electron bunch with an energy of a few hundreds ofMeV. This phenomenon, which is referred to as laser-wakefield acceleration, has many potential applications, including the design of ultra-bright X-ray sources known as freeelectron lasers (FEL). However, these applications require the electronbunch to have an excellent quality (low divergence, emittance andenergy spread). In this thesis, different solutions to improve thequality of the electron bunch are developed, both analytically and through the use of Particle-In-Cell (PIC) simulations. It is first shown however that PIC simulations tend to erroneously overestimate the emittance of the bunch, due to the numerical Cherenkov effect. Thus, in order to correctly estimate the emittance, a modified PICalgorithm is proposed, which is not subject to this unphysical Cherenkov effect. Using this algorithm, we observed and studied a new mechanism togenerate the electron bunch: optical transverse injection. This mechanism can produce bunches with ahigh charge, a low emittance and a low energy spread. In addition, wealso proposed an experimental setup - the laser-plasma lens- which can strongly reduce the final divergence of the bunch. Finally, these results are put into context by discussing the propertiesrequired for the design of a compact FEL. It is shown in particularthat laser-wakefield accelerator could be advantageously combinedwith innovative laser-plasma undulators, in order to produce brightX-rays sources
23
Short, Lee R. "Damage produced by the free electron laser." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA366898.
Повний текст джерелаАнотація:
Thesis (M.S. in Applied Physics) Naval Postgraduate School, June 1999."June 1999". Thesis advisor(s): William B. Colson, Robert L. Armstead. Includes bibliographical references (p. 57). Also available online.
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McGinnis, Roger D. "Free Electron Laser development for directed energy." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA387898.
Повний текст джерелаАнотація:
Dissertation (Ph.D. in Physics) Naval Postgraduate School, Dec. 2000.Dissertation advisor, Colson, William B. "December 2000." Includes bibliographical references (p. 131-133). Also available in print.
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Malton, S. P. "Laser interactions with high brightness electron beams." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1444964/.
Повний текст джерелаАнотація:
The International Linear Collider will be a high-precision machine to study the next energy frontier in particle physics. At the TeV energy scale, the ILC is expected to deliver luminosities in excess of 1034 cni" 2s_1. In order to achieve this, beam conditions must be monitored throughout the machine. Measurment of the beam emittance is essential to ensuring that the high luminosity can be provided at the interaction point. At the de sign beam sizes in the ILC beam delivery system, the Laserwire provides a non-invasive real-time method of measuring the emittance by the method of inverse Compton scattering. The prototype Laserwire at the PETRA stor age ring has produced consistent results with measured beam sizes of below 100 /nn. The Energy Recovery Linac Prototype (ERLP) is a technology testbed for the 4th Generation Light Source (4GLS). Inverse Compton scattering can be used in the ERLP as a proof of concept for a proposed 4GLS upgrade, and to produce soft X-rays for condensed matter experiments. The design constraints for the main running mode of the ERLP differ from those required for inverse Compton scattering. Suitable modifications to the optical lattice have been developed under the constraint that no new magnetic structures may be introduced, and the resulting photon distributions are described.
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Huo, Yijie. "Experimental study of laser produced electron beam." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1858.
Повний текст джерелаАнотація:
Thesis (M.S.) -- University of Maryland, College Park, 2004.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Reed, Valerie Christine. "Electron motion in ultra-intense laser fields." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293544.
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Harvey, Christopher. "Electron dynamics in high-intensity laser fields." Thesis, University of Plymouth, 2010. http://hdl.handle.net/10026.1/301.
Повний текст джерелаАнотація:
We consider electron dynamics in strong electromagnetic fields, such as those expected from the next generation of high-intensity laser facilities. Beginning with a review of constant classical fields, we demonstrate that the electron motion (as given by the Lorentz force equation) can be divided into one of four Lorentz invariant cases. Parameterising the field tensor in terms of a null tetrad, we calculate the radiative energy spectrum for an electron in crossed fields. Progressing to an infinite plane wave, we demonstrate how the electron orbit in the average rest frame changes from figure-of-eight to circular as the polarisation changes from linear to circular. To move beyond a plane wave one must resort to numerics. We therefore present a novel numerical formulation for solving the Lorentz equation. Our scheme is manifestly covariant and valid for arbitrary electromagnetic field configurations. Finally, we reconsider the case of an infinite plane wave from a strong field QED perspective. At high intensities we predict a substantial redshift of the usual kinematic Compton edge of the photon emission spectrum, caused by the large, intensity dependent effective mass of the electrons inside the laser beam. In addition, we find that the notion of a centre-of-mass frame for a given harmonic becomes intensity dependent.
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McKenna, Paul. "Electron and laser interactions with positive ions." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326350.
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Penman, Charles. "Theoretical studies of the free-electron laser." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47218.
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Wong, Liang Jie. "Laser-driven electron acceleration in infinite vacuum." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66479.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 83-88).
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.
by Liang Jie Wong.
S.M.
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Robinson, David Jonathan. "Atomic electron dynamics in intense laser fields." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675426.
Повний текст джерелаАнотація:
Electron dynamics in laser-driven one- and two-electron atoms and ions are probed through numerical integration of the full -dimensional, time-dependent Schro"dinger Equation. Physical observables, such as ionization rates and the spectrum of harmonics generated by the system, are extracted from the wavefunction. For an atom in a one-colour, linearly polarized laser field, wavepackets ejected at certain times will recoillide with the core, generating harmonics of the driving field. The harmonic spectrum is calculated using HELIUM and used to benchmark those from the time-dependent R-matrix (TDRM) method and a single-active-electron (SAE) code. HELIUM and TDRM results agree to within 20% while SAE calculations agree in the high-frequency region of the spectrum. The two-photon double ionization (TPDI) cross section of helium is calculated for frequencies 40 eV<ω< 54 a.u. In this frequency range, sequential ionization requires the absorption of three photons while non-sequential ionization is a two-photon process so that the latter mechanism is dominant for fields with low intensity. The cross section is shown to be sensitive to pulse duration, especially near the 54 eV threshold. Calculations using the HELIUM code provide TPDI cross sections accurate to a few percent across the whole frequency range. Extension of the method to treat one-electron atoms and ions in orthogonally polarized, two-colour laser fields are described. An orthogonally polarized, two-colour field will steer ionized wavepackets in the continuum. The likelihood of recollision, and the recolliding wavepackets velocity are significantly changed. These effects can be seen in the harmonic spectrum. Such a two-colour scheme has been proposed as a way to image complex molecular orbitals. The harmonic spectrum from model atomic systems in such fields is calculated. It is observed that the harmonic spectrum is sensitive to the symmetry of the electron orbitals. Thus, for the 2p state even harmonics are significantly stronger than those in the 2s case.
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Gillingham, David R. "Free electron laser single-particle dynamics theory." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA246245.
Повний текст джерелаАнотація:
Thesis (M.S. in Physics)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Colson, William B. Second Reader: Maruyama, Xavier K. "December 1990." Description based on title screen as viewed on March 31, 2010. DTIC Identifier(s): Free Electron Lasers, Computerized Simulations, Parmela Computer Programs, Cray Computers, Theses. Author(s) subject terms: Free Electron Lasers, Computerized Simulation. Includes bibliographical references (p. 52-53). Also available in print.
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Cortelli, Giorgio. "Ultrafast electron diffraction on materials exposed to intense free electron laser pulses." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19305/.
Повний текст джерелаАнотація:
The advent of Free Electron Lasers (FELs) has opened unprecedented opportunities for the study of transient states of matter. The use of the seeding technique, developed at the FERMI FEL in Trieste (Italy), pushed further the frontier allowing to perform pump-probe experiments with femtosecond time resolution. FELs permit shedding light onto unexplored non-equilibrium dynamics and processes in matter. In this thesis, a pioneering setup for monitoring sub-picosecond atomic structure changes in materials is described. The FEL is used as an isochoric pump while a 100 keV compressed electron bunch is used as a structural probe thus obtaining an ultrafast electron diffraction (UED) facility. Results of a pilot UED experiment on selected samples (gold and diamond) are presented and analysed.
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Armstrong, G. S. J. "Electron dynamics of one- and two-electron atoms in intense laser fields." Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546004.
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Shen, Nainn-Tzuu. "Evolution of the electron beam envelope in a free electron laser beamline." Thesis, Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/39013.
Повний текст джерелаАнотація:
Approved for public release; distribution is unlimited.The free electron laser (FEL) is a new generation of laser whose development motivates further research in basic and applied physics. Unlike a conventional laser that uses a gas or solid state gain medium, the FEL gain medium is a relativistic electron beam produced by a particle accelerator. This thesis will explore electron beam dynamics in an FEL, including the beam envelope equation, which will help us understand the evolution of electron betatron motion in the undulator. Dipole magnets, quadrupoles, and solenoids play important roles in transporting and focusing in an FEL beamline. The dipole magnets redirect the electron beam to a beam dump or recirculate the electrons for energy recovery. The quadrupoles and solenoids collimate and focus the electron beam. Simulations and theory are used to model and study a simple FEL beamline.
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Maroju, Praveen Kumar [Verfasser], and Giuseppe [Akademischer Betreuer] Sansone. "Attosecond pulse shaping at a seeded free-electron laser : : towards attosecond time-resolved experiments at the free-electron lasers." Freiburg : Universität, 2021. http://d-nb.info/1239556527/34.
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Hannon, Fay. "A high average-current electron source for the Jefferson Laboratory free electron laser." Thesis, Lancaster University, 2008. http://eprints.lancs.ac.uk/76588/.
Повний текст джерелаАнотація:
The spectral output power from the Jefferson Laboratory infra-red free electron laser is primarily limited by the performance of the electron injector. Free electron laser power is directly proportional to the electron beam current and at present the electron injector is limited to 10mA average current. To date the highest laser power achieved has been 14.2kW and the next goal is to reach 100kW. For this to occur a new electron injector has been designed that is capable of producing over 100mA average current. This thesis describes an investigation into the behaviour of this injector through simulation. Given that the layout of the injector is fixed, this thesis aims to find suitable operating regimes for various electron bunch charge scenarios. By determining the important features the electron beam must have at the exit of the injector, and the limitations of each component, this information was used to form an optimisation problem that could be solved to find the best operation point. To improve the simulation of electron bunches being launched from a photocathode, measurements were performed on a similar injector to evaluate the thermal energy and response time of the cathode. These values are a function of the laser wavelength used with the photocathode and so were repeated over a range of wavelengths from infra-red to green. The injector at Cornell University was used to take measurements of the electron beam that could then be compared against simulation to benchmark the code. The brightness and quality of electron beams in linac-based light sources, such as at Jefferson Laboratory, are limited by the properties of the beam in the injector. It is therefore important to have knowledge of the phase space distribution of the electron beam in addition to the rms emittance, to provide an insight into high brightness formation mechanisms. A tomography technique has been successfully used to reconstruct the transverse phase space of the electron beam delivered from the Cornell University ERL DC gun. The gun is similar to that in the 100mA JLab injector, therefore a tomography diagnostic could in future be applied to that case.
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Tzoufras, Michail. "Generation of multi-giga-electron-volt monoenergetic electron beams via laser wakefield acceleration." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1634233741&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Kamps, Thorsten. "Monitoring the electron beam position at the TESLA Test Facility Free Electron Laser." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2000. http://dx.doi.org/10.18452/14502.
Повний текст джерелаАнотація:
Der Betrieb eines Freien Elektronen Lasers (FEL), bei dem die spontan emittierte Undulatorstrahlung ueber Wechselwirkung mit dem Elektronenstrahl selbst verstaerkt wird, setzt eine praezise Ausrichtung des Elektronenstrahls mit dem Photonenstrahl voraus. Um den Ueberlapp von Elektronen-und Photonenstrahl zu gewaehrleisten, wurde ein neuartiger Typ von Wellenleiter-Strahllagemonitor entwickelt, der in eine Vakuumkammer des Undulators des FELs der TESLA Test Facility (TTF) integriert ist. Vier um das Strahlrohr verteilte Wellenleiter koppeln ueber schmale Schlitze einen Bruchteil jenes elektromagnetischen Feldes aus, welches den Strahl begleitet. Die induzierten Signale haengen von der transversalen Strahlposition und der Strahlintensitaet ab. Mit vier Schlitz-Wellenleiter Paaren laesst sich ein lineares Signal ableiten, anhand dessen die Position des Elektronenstrahls bestimmt werden kann. Die induzierten Signale werden mittels eines stegbelasteten Wellenleiters in die erste Stufe eines bei 12 GHz arbeitenden Empfaengers zugefuehrt. Die vorliegende Arbeit beschreibt Design, Tests und Implementierung dieses neuartigen Typs von Strahllagemonitor.The operation of a free electron laser working in the Self Amplified Spontaneous Emission mode (SASE FEL) requires the electron trajectory to be aligned with very high precision in overlap with the photon beam. In order to ensure this overlap, one module of the SASE FEL undulator at the TESLA Test Facility (TTF) is equipped with a new type of waveguide beam position monitor (BPM). Four waveguides are arranged symmetrically around the beam pipe, each channel couples through a small slot to the electromagnetic beam field. The induced signal depends on the beam intensity and on the transverse beam position in terms of beam--to--slot distance. With four slot--waveguide combinations a linear position sensitive signal can be achieved, which is independent of the beam intensity. The signals transduced by the slots are transferred by ridged waveguides through an impedance matching stage into a narrowband receiver tuned to 12 GHz. The present thesis describes design, tests, and implementation of this new type of BPM.
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Ng, Ivan Y. C. "A free electron laser weapon for sea archer." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA401554.
Повний текст джерелаАнотація:
Thesis (M.S. in Applied Physics) Naval Postgraduate School, Dec. 2001.Thesis advisor(s): Colson, William B.; Armstead, Robert L. "December 2001." Includes bibliographical references (p. 57-58). Also available in print.
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Neumann, Jonathan G. "Laser switched electron beam modulation with terahertz applications." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2437.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Electrical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Tang, Yew Fei. "Electron field emission from laser crystallised amorphous silicon." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/843179/.
Повний текст джерелаАнотація:
Flat panel displays based on electron field emission can provide the benefits of the high resolution of a cathode ray tube display while possessing the portability of a liquid crystal display. To date, the problem with a field emission flat panel display based on silicon is that it usually involves complex photolithography processing, making it too complex and expensive to be commercially viable. In this thesis, the emphasis of the research is to fabricate a three terminal silicon device for flat panel display based on field emission technology without using photolithography processes. Laser crystallised amorphous silicon is chosen for our material which creates a rough silicon surface whose roughness gives rise to field enhancement. Furthermore, this process is widely used in the display industry to fabricate silicon based display driver thin film transistors, which can be readily incorporated. It is important to understand the electron field emission mechanism from the laser crystallised amorphous silicon and to find optimum conditions for emission. In the course of our research, we established a regime for super sequential lateral growth or a hybrid sequential lateral solidification and super lateral growth in Nd:YAG crystallisation of amorphous silicon. Excimer laser crystallised amorphous silicon under optimum conditions gives emission currents of the order of 10-5A (current densities ~ 0.04 A/cm2) at threshold fields less than 15 V/mum in a diode configuration, without the need for a forming process. Through experiments, we concluded that the field emission mechanism from these samples is not controlled purely by surface phenomena, contrary to what was suggested by the Fowler Nordheim theory. Instead, it is the diffusion of the underlay metals into the silicon that create clusters of silicide that allow the electrons to become "hot" while travelling between the clusters. Lastly, a novel process illustrating that a three-terminal device based on laser crystallised amorphous silicon can be fabricated without the need for photolithography. However, the field emission data showed that some fine-tuning of the process is still required.
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Kampouridis, Anastasios. "Laguerre-Gaussian modes in the free electron laser." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Jun%5FKampouridis.pdf.
Повний текст джерелаАнотація:
Thesis (M.S. in Physics)--Naval Postgraduate School, June 2007.Thesis Advisor(s): William B. Colson, Robert L. Armstead. "June 2007." Includes bibliographical references (p. 71-72). Also available in print.
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Zimmer, Aaron A. "Terahertz free-electron laser optical design and simulation." Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/5328.
Повний текст джерелаАнотація:
Approved for public release; distribution is unlimitedThe Free Electron Laser (FEL) provides a versatile method for producing laser light. Traditionally, FELs are complicated in design and occupy large research facilities. The primary goal of this thesis is to investigate a particular FEL design that is small in size and operates in the terahertz (THz) frequency regime. The optics materials requirements are explored for power levels ranging from mW to kW. Additionally, as part of a simpler design and in spite of the large amount of diffraction present at THz wavelengths, a waveguide will not be utilized as others have done previously. Laser beam clipping, which is defined as the absorption of the laser beam at the outer edges of the diffracted mode, and a shortened undulator are investigated as methods to support the elimination of the waveguide.
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Kiel, David H. "Two nonlinear models of the Free Electron Laser." Thesis, Monterey, California. Naval Postgraduate School, 1990. http://hdl.handle.net/10945/30622.
Повний текст джерелаАнотація:
Approved for public release, distribution unlimitedThe dynamics of the Free Electron Laser are governed by Maxwell's equations which causes many highly nonlinear regimes to exist in Free Electron Laser Physics. This thesis will examine two such areas and develop simple models to describe the highly dynamic and rich behavior two of these regimes. In the strong-field, high current regime, the Free Electron Laser driving current can be modeled by a single macroparticle representing the trapped electrons. When the trapped electrons act collectively as a macroparticle representing the trapped electrons. When the trapped electrons act collectively as a macroparticle, solutions which include synchrotron oscillations can be found for the self-consistent pendulum and wave equations. In an FEL oscillator with low single-pass gain, the evolution of the optical wave can lead to sideband development. This phenomenon is studied by applying Maxwell's equations to an oscillator with two optical modes and deriving a two-mode wave and pendulum equation. The two-mode wave and pendulum equations are implemented numerically on computers so that the onset of the sideband can be explored.
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Pogue, Conor Michael. "Super-radiant free electron laser measurement and detection." Thesis, Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/37696.
Повний текст джерелаАнотація:
Approved for public release; distribution is unlimitedA free electron laser (FEL) is a type of laser that use relativistic electron bunches and a periodic magnetic field to generate coherent radiation. These types of lasers are of interest to the Navy because they can operate at the high average power with excellent optical beam quality that is needed in many military applications. A current project between the U.S. Navy and Niowave Inc. is to create a super-radiant FEL that uses superconducting spoke cavities for the electron accelerating structures. These types of cavities have never been used in an FEL before and may be more suitable for deployment on naval platforms due to their smaller size and structural rigidity compared to more conventional cavities. Furthermore, spoke cavities allow operation at lower accelerating frequencies while still maintaining reasonable size cavities, which may reduce power requirements for the cryoplant. This thesis will discuss variety of optical transport and detection arrangements for various setups and FEL operational regimes.
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Pogue, Conor M. "Terahertz free electron laser: design, simulation and analysis." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/44646.
Повний текст джерелаАнотація:
Approved for public release; distribution is unlimitedTerahertz (THz) radiation is a portion of the electromagnetic spectrum with many potential uses but without a wide availability of powerful sources. The free electron laser (FEL) has been demonstrated to produce intense, coherent THz radiation. This dissertation explores a novel THz FEL oscillator design that is tunable within a wavelength range of ~60 micrometers to ~130 micrometers and could produce up to ~2 kW average output power. It utilizes superconducting spoke cavities for the accelerating structures to generate an 8 MeV electron beam with ~8.75mA average current. The variable gap undulator has only ten periods; this design choice enhances the extraction and therefore output power, but also reduces single pass gain. To overcome the reduced gain, the optical cavity is designed to minimize round trip losses. This design is relatively compact and could be installed on a ship to test technologies that are relevant for future scaling to weapons class output powers.
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Cheng, Chunwei. "The development of the UK free-electron laser." Thesis, Heriot-Watt University, 1987. http://hdl.handle.net/10399/1016.
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Findlay, Peter Charles. "Free electron laser spectroscopy of narrow gap semiconductors." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/528.
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