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Schreiber, Jörg. "Ion Acceleration driven by High-Intensity Laser Pulses." Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-58421.
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Schreiber, Jörg. "Ion acceleration driven by high-intensity laser pulses." [S.l.] : [s.n.], 2006. http://edoc.ub.uni-muenchen.de/archive/00005842.
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Naughton, Kealan. "Characterization and optimization of laser-driven ion acceleration." Thesis, Queen's University Belfast, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.728382.
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Henig, Andreas. "Advanced Approaches to High Intensity Laser-Driven Ion Acceleration." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-114831.
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Carroll, David C. "Laser-driven ION acceleration : source optimisation and optical control." Thesis, University of Strathclyde, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501894.
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Bin, Jianhui. "Laser-driven ion acceleration from carbon nano-targets with Ti:Sa laser systems." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-185199.
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Over the past few decades, the generation of high energetic ion beams by relativistic intense laser pulses has attracted great attentions. Starting from the pioneering endeavors around 2000, several groups have demonstrated muliti-MeV (up to 58 MeV for proton by then) ion beams along with low transverse emittance and ps-scale pulse duration emitted from solid targets. Owing to those superior characteristics, laser driven ion beam is ideally suitable for many applications. However, the laser driven ion beam typically exhibits a large angular spread as well as a broad energy spectrum which for many applications is disadvantageous.
The utilization of nano-targets as ion source provides a number of advantages over micrometer thick foils. The presented PhD work was intended to investigate laser driven ion acceleration from carbon nano-targets and demonstrate the potential feasibility for biological studies. Two novel nano-targets are employed: nm thin diamond-like-carbon (DLC) foil and carbon nanotubes foam (CNF). Both are self-produced in the technological laboratory at Ludwig-Maximilians-Universität München. Well-collimated proton beams with extremely small divergence (half angle) of 2 degrees are observed from DLC foils, one order
of magnitude lower as compared to micrometer thick targets. Two-dimensional particle-in-cellsimulations indicate a strong influence from the electron density distribution on the divergence of protons. This interpretation is supported by an analytical model. In the same studies, the highest maximum proton energy was observed with a moderate laser intensity as low as 5*10^18W/cm^2. Parallel measurements of laser transmission and reflection are used to determine laser absorption in the nano-plasma, showing a strong correlation to the maximum proton energy. This observation indicates significance of absorbed laser energy rather than incident laser intensity and is supported by an analytical model. The ion energy also depends on pulse duration, a reduced optimum pulse duration is found as compared to micrometer thick targets. This behavior is attributed to a reduction of transverse electron spread due to the reduction of thickness from micrometer to nanometer. These remarkable proton bunch characteristics enabled irradiating living cells with a single shot dose of up to 7 Gray in one nanosecond, utilizing the Advanced Titanium: sapphire LASer (ATLAS)system at Max-Planck-Institut of Quantum Optics (MPQ). The experiments represent the first feasibility demonstration of a very compact laser driven nanosecond proton source for radiobiological studies by using a table-top laser system and advanced nano-targets.
For the purpose of providing better ion sources for practical application, particularly in terms of energy increase, subsequent experiments were performed with the Astra Gemini laser system in the UK. The experiments demonstrate for the first time that ion acceleration can be enhanced by exploiting relativistic nonlinearities enabled by micrometer-thick CNF targets. When the CNF is attached to a nm-thick DLC foil, a significant increase of maximum carbon energy (up to threefold) is observed with circularly polarized laser pulses. A preferable enhancement of the carbon energy is observed with non-exponential spectral shape, indicating a strong contribution of the radiation pressure to the overall acceleration. In contrast, the linear polarization give rise to a more prominent proton acceleration. Proton energies could be increased by a factor of 2.4, inline with a stronger accelerating potential due to higher electron temperatures. Three-dimensional (3D) particle-in-cell (PIC) simulations reveal that the improved performance of the double-layer targets (CNF+DLC) can be attributed to relativistic self-focusing in near-critical density plasma. Interestingly, the nature of relativistic non-linearities, that plays a major role in laserwakefield-acceleration of electrons, can also apply to the benefit of laser driven ion acceleration.
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Prasad, Rajendra. "Ion acceleration driven by ultra-short ultra-intense laser pulses." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602926.
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Laser driven ion sources are being foreseen as promising candidate for many potential applications. This thesis presents the results of ion acceleration investigated in the regime of ultra-high intensity (>1020 W/cm2). ultra -short (50 fs) and ultra-high contrast laser pulse interaction with solid density targets. The efficiency of ion acceleration in this unique condition was studied by varying various laser and target parameters. The energy scaling and spectral features were investigated at oblique and normal laser incidence. Under oblique incidence, the dependence of maximum cut-off energy of the protons and ion flux of the accelerated particles on the target thickness (50 nm- 6pm) were investigated. A comparison of ion flux at oblique incidence with ion flux at normal incidence was performed. The conversion efficiency of laser energy into proton energies was estimated. At normal incidence, with ultra-thin so lid targets (10-100 nm), a possible emergence of the radiation pressure acceleration scenario was observed. In the proton spectra, quasimonoenergetic peak centred around 10 MeV was observed. The energy of the protons at peak followed the energy scaling of the RPA process in the non-relativistic limit. These features were corroborated by 20 PIC simulations. The maximum cut-off energies dependence of the accelerated ions was investigated by varying target thickness for linear and circular polarisations. Cut-off energies of 20 MeV/u for both the protons and (6+ were obtained. The interaction of ultra-short, intense laser pulses with spray targets was studied. In the previous experiments using water spray, observation of negative ions was explained by electroncapture an~ loss processes, and acceleration of neutral oxygen atoms with similar energies was also suggested. The neutrals were measured employing a time of flight technique. The concept of generation of negative ions was verified by a novel method where positive ions produced from foil target propagated through the cold spray medium, producing negative ions. A new ethanol spray was also characterised. The irradiation of this new spray target with intense laser produced negative carbon ions in addition to the negative oxygen ions. Moreover, negative hydrogens were also observed. The acceleration of quasi-monoenergetic protons with energy, 2.8t,O.3 MeV observed from water spray is also discussed simulations.
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Dover, Nicholas. "Exploring novel regimes for ion acceleration driven by intense laser radiation." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/39343.
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This thesis covers experimental and numerical studies on novel schemes of ion accelera- tion with high intensity lasers. In particular, it discusses previously unexplored regimes incorporating the radiation pressure of intense lasers. These schemes are of interest to potential applications due to the emergence of improved ion beam properties that are detailed in this thesis. The thesis discusses results from ion acceleration experiments using intense optical lasers on ultra-thin targets at the Rutherford Appleton Laboratory, where the Vulcan Petawatt system was used to irradiate nanometre thickness foils. In particular, the accelerated proton beam profiles from these interactions showed a variety of features, such as Rayleigh-Taylor-like instability driven spatial beam modulation, annular rings and a high-energy tail. A particularly interesting novel observation is the emergence of a spectrally peaked on-axis component to the proton beam, which is indicative of buffering of the proton layer ahead of a heating heavier ion species. These different features will be analysed and discussed, and modelled using PIC simulation. The thesis also includes the results from recent experiments studying the interaction of an intense CO2 laser with an overdense plasma generated by a gas jet. A remarkably monoenergetic proton beam was measured, in contrast to the majority of experiments performed previously on ion acceleration, and was found by optical probing and numer- ical simulation to be a result of hole-boring generated by the radiation pressure of the intense laser pulse acting on the plasma. The thesis will include analysis of interferometry and shadowgraphy images of the plasma, and discussion of the plasma dynamics and ion generation mechanisms involved, including the generation of radiation pressure driven collisionless shock waves. The effects of the laser prepulse, electron transport effects and non-linear post-soliton production will all be discussed. It will also present detailed numerical particle-in-cell (PIC) simulation of the interaction.
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Padda, Hersimerjit. "Intra-pulse dynamics of laser-driven ion acceleration in ultra-thin foils." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28657.
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This thesis reports on experimental and numerical investigations of ion acceler-ation driven by the interaction of short, intense laser pulses with ultra-thin, solid targets in which relativistic transparency is induced. In particular, it explores the multiple laser-ion acceleration mechanisms that take place over the duration of the laser pulse. Investigating these acceleration mechanisms is important for understanding the underlying physical dynamics and optimising laser-driven ion acceleration. The investigations featured in this thesis result from intense laser-solid in-teractions conducted at the Rutherford Appleton Laboratory, using the Vulcan Petawatt laser system. The first investigation explores the spatial-intensity profile of the proton beam accelerated from thin (tens of nanometre) aluminium targets. The beam of accelerated protons displayed a variety of features, including a low-energy annular profile, a high energy component with a small divergence and Rayleigh-Taylor-like instabilities. A particularly interesting observation is the low-energy annular profile, which is shown to be sensitive to target thickness and proton energy. Numerical investigations using particle-in-cell (PIC) simulations exhibit the same trends and demonstrate that the radiation pressure from the laser pulse drives an expansion of the target ions within the spatial extent of the laser focal spot. This induces a radial deection of relatively low energy sheath-accelerated protons to form an annular distribution. Through variation of the target foil thickness, the opening angle of the ring is shown to be correlated to the point in time during the laser pulse interaction at which the target becomes transparent to the laser (in a process termed relativistic induced transparency). The ring is largest when transparency occurs close to the peak of the laser intensity. The second investigation focuses on the rising edge profile of the laser pulse and the correlation between its temporal width and the resultant maximum proton energy. An important parameter to consider when irradiating nanometre-thick foils is the laser contrast. However, the effect of the temporal width of the laser pulse at 1% of the peak, where the intensity is ~1018 Wcm-2, has not been previously explored. Using CH targets with a fixed thickness, a range of proton energies, from 20-70 MeV, are measured experimentally. The temporal width ofthe laser pulse is measured using a second order autocorrelator and is used to model the rising edge of the laser pulse on target. The temporal width at 50%, 10% and 1%, of the peak of the pulse, is measured. The measured proton energies are found to strongly correlate with the temporal width at the 1% level, and as the duration at this pulse width increased the maximum proton energy decreased. Using particle-in-cell simulations, a detailed numerical investigation is carried out to understand the effect the rising edge of the laser pulse has on proton energies. By increasing the temporal width at 1%, the expansion of the target increased, resulting in a less efficient acceleration of protons. Furthermore, by inducing a small expansion in the target before the peak of the pulse arrives, the hole boring mechanism of RPA can be optimised along the laser axis. However, in the case where the temporal width at 1% is relatively larger, the hole boring mechanism no longer dominates the interaction, as the target undergoes relativis-tic induced transparency on the rising edge of the pulse, limiting the effect of hole boring. Improving the laser contrast on the picosecond time-scale could result in higher and stable proton energy.
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Bin, Jianhui [Verfasser], and Jörg [Akademischer Betreuer] Schreiber. "Laser-driven ion acceleration from carbon nano-targets with Ti:Sa laser systems / Jianhui Bin. Betreuer: Jörg Schreiber." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2015. http://d-nb.info/107545672X/34.
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Puyuelo, valdes Pilar. "Laser-driven ion acceleration with high-density gas-jet targets and application to elemental analysis." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0134.
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Cette thèse en cotutelle entre la France et le Canada étudie l’accélération d’ions dans l’interaction laser-plasma. La première partie, réalisée au CENBG et sur l’installation PICO2000 du laboratoire LULI à l'École Polytechnique de Palaiseau, présente des études expérimentales, complétées par des simulations numériques de type Particle-In-Cell, portant sur l’accélération d’ions dans l'interaction d'un laser infrarouge de haute puissance avec une cible gazeuse de haute densité. La seconde, réalisée avec le laser ALLS de l’institut EMT INRS, concerne le développement d'une application des faisceaux génerés par laser pour l’analyse élémentaire d’échantillons. Dans le manuscrit, les caractéristiques des deux lasers, des différents diagnostics de particules et d’X utilisés (paraboles de Thomson, films radiochromiques, CCD...) ainsi que les configurations expérimentales sont décrites.Les jets de gaz denses supersoniques utilisés comme cibles d'interaction laser au LULI, sont présentés en détail; depuis leur conception grâce à des simulations de dynamique des fluides, jusqu’à la caractérisation de leurs profils de densité par interférométrie Mach Zehnder. D'autres méthodes optiques comme la strioscopie ont été mises en œuvre pour contrôler la dynamique du jet de gaz et définir l’instant optimal pour effectuer le tir laser. Les spectres obtenus dans differentes conditions d’interaction sont présentés. Ils montrent, dans la direction du laser, des énergies maximales allant jusqu’à 6 MeV pour les protons et 16 MeV pour les ions hélium. Des simulations numériques effectuées avec le code PICLS sont utilisées pour discuter les différentes structures observées dans les spectres et les mécanismes d’interaction sous jacents.Des faisceaux de protons et d’X générés par le laser ALLS dans l’interaction avec des cibles solides d’aluminium, de cuivre et d’or ont été utilisés pour effectuer des analyses de matériaux par les méthodes Particle-induced X-ray emission (PIXE) et X-ray fluorescence (XRF). L’importance relative des deux techniques, XRF et PIXE, est étudiée en fonction de la nature de la cible d’interaction. Les deux diagnostics peuvent être implémentés simultanément ou individuellement, en changeant simplement la cible d'interaction. La double contribution des deux processus améliore l’identification des constituants des matériaux et permet une analyse volumétrique jusqu'à des dizaines de microns et sur de grandes surfaces (~cm2) jusqu'à un seuil de détection de quelques ppmsIn this joint thesis, performed between the French Institute CENBG (Bordeaux) and the Canadian Institute INRS (Varennes), laser driven ion acceleration and an application of the beams are studied. The first part, carried out at CENBG and on the PICO2000 laser facility of the LULI laboratory, studies both experimentally and using numerical particle-in-cell (PIC) simulations, the interaction of a high power infrared laser with a high density gas target. The second part, performed at ALLS laser facility of the EMT-INRS institute, investigates the utilization of laser generated beams for elementary analysis of various materials and artifacts. In this work, firstly the characteristics of the two lasers, the experimental configurations, and the different employed particle diagnostics (Thomson parabolas, radiochromic films, etc.) employed are introduced.In the first part, a detailed study of the supersonic high density gas jets which have been used as targets at LULI is presented, from their conceptual design using fluid dynamics simulations, up to the characterization of their density profiles using Mach-Zehnder interferometry. Other optical methods such as strioscopy have been implemented to control the dynamics of the gas jet and thus define the optimal instant to perform the laser shot. The spectra obtained in different interaction conditions are presented, showing maximum energies of up to 6 MeV for protons and 16 MeV for Helium ions in the laser direction. Numerical simulations carried out with the PIC code PICLS are presented and used to discuss the different structures seen in the spectra and the underlying acceleration mechanisms.The second part presents an experiment using laser based sources generated by the ALLS laser to perform a material analysis by the Particle-induced X-ray emission (PIXE) and X-ray fluorescence (XRF) techniques. Proton and X-ray beams produced by the interaction of the laser with Aluminum, Copper and Gold targets were used to make these analyzes. The relative importance of XRF or PIXE is studied depending on the nature of the particle production target. Several spectra obtained for different materials are presented and discussed. The dual contribution of both processes is analyzed and indicates that a combination improves the retrieval of constituents in materials and allows for volumetric analysis up to tens of microns on cm^2 large areas, up to a detection threshold of ppms
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Kakolee, Kaniz Fatema. "Laser driven acceleration of ions and its application in radiobiology." Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.579733.
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Carrier-Vallieres, Simon. "Towards reliable, intense and high repetition-rate laser-driven ion beamlines." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0224.
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Les accélérateurs de particules attirent beaucoup d’attention en raison de leur nombreuses applications dans des domaines allant des sciences fondamentales, à la médecine jusqu’aux applications industrielles. Ces travaux de doctorat se situent au premier plan du développement des sources d’ions générées par laser, afin de les rendre plus compétitives face aux accélérateurs conventionnels. Pour ce faire, les sources d’ions obtenues par laser doivent être compactes, efficaces par rapport aux coûts, fiables, intenses et opérées à des taux de répétition élevés. L’effort général de ces travaux de doctorat vise à pousser leur performance sur trois fronts, soit l’alignement précis des cibles, l’amélioration des cibles à l’aide de nanostructures ainsi que le développement de détecteurs de particules efficients. Cette quête d’efficacité accrue a requis des travaux autant numériques, par l’utilisation de Calcul de haute performance, qu’expérimentaux, par le montage d’une ligne d’accélération d’ions de pointe sur les installations de l’Advanced Laser Light Source (ALLS) 100 TW ainsi qu’en effectuant plusieurs campagnes expérimentales à l’étranger.Les travaux visent d’abord à augmenter la fiabilité des faisceaux d’ions par le positionnement précis des cibles solides utilisées en accélération d’ions par laser. Pour ce faire, un interféromètre de positionnement des cibles (Target Positioning Interferometer, TPI), atteignant une précision d’alignement sous-micrométrique, a été développé. Le design novateur du TPI est un interféromètre de Michelson modifié dans lequel nous avons introduit une lentille convergente asphérique dans le bras de la cible, afin de le transformer en un système de positionnement absolu ayant un unique point d’inambiguïté dans l’espace. La fine capacité d’alignement du TPI est atteinte également avec l’aide d’un algorithme numérique d’analyse des franges d’interférences qui maximise l’extraction de signaux à grand rapport signal-sur-bruit, effectuée dans une fenêtre de temps optimisée.La deuxième partie des travaux concerne le rehaussement du mécanisme d’accélération, permettant de générer de plus grandes quantités d’ions à des plus hautes énergies cinétiques, menant à des faisceaux d’ions plus intenses. Les cibles solides typiquement utilisées sont des feuilles métalliques minces, limitant l’efficacité de conversion d’énergie du laser aux ions à quelques pourcents tout au plus. Une façon d’augmenter cette efficacité de conversion est en nanostructurant la surface des cibles afin d’emprisonner l’onde incidente, augmentant ainsi le transfert d’énergie aux ions. Nous avons démontré, de façon théorique et expérimentale, qu’un ajustement optimal des paramètres géométriques des nanostructures, en particulier avec des nanosphères et des nanofils, mène à une augmentation du nombre d’ions et de leur énergies cinétiques de plusieurs fois les valeurs obtenues avec le même pulse laser incident sur une cible plane faite du même matériau.Dans la dernière partie, les travaux sont orientés sur le développement de détecteurs de particules efficients afin d’être implémentés sur les lignes d’accélération d’ions à haut taux de répétition. Une calibration en nombre absolu des nouveaux films radiochromiques EBT-XD a d’abord été effectuée. Il a été observé que les EBT-XD offrent une plus grande plage de mesure de dose ainsi qu’un seuil minimum d’énergie de détection plus élevé que leur homologue EBT3, étant donc mieux adaptés pour les lignes d’ions plus intenses. Nous avons également mesuré une sévère inhibition de la réponse des EBT-XD lorsque le pic de Bragg de la particule mesurée tombe directement dans la couche active des films, causant des erreurs importantes dans l’estimation du nombre de particules. Finalement, nous avons implémenté, sur la ligne d’accélération d’ions d’ALLS 100 TW, un système de détecteurs de particules calibrés en croisés incluant un spectromètre à parabole Thomson (TP) ainsi que deux en temps de volParticle accelerators attract a lot of attention in the scientific and non-scientific community as a result of their wide applicability in fields ranging from fundamental sciences, medicine to industrial applications. This doctoral work stands at the forefront of laser-based ion accelerators, and pushes forward their development to make them more competitive ion sources compared to conventional particle accelerators. For achieving higher competitiveness, laser-driven ion sources must be compact, cost-effective, reliable, intense and operated at high repetition-rates, which all together yield ion beam characteristics that cannot be realistically matched by any other kind of ion accelerator. To do so, the general effort of this doctoral work tackled three different aspects of laser-based ion acceleration, namely precise target alignment, improved targetry using nanostructures and the development of efficient particle diagnostics. The endeavor required to perform equivalent amounts of numerical work, through simulations using High Performance Computing, as well as experimental work, by implementing a cutting-edge ion beamline at the Advanced Laser Light Source (ALLS) 100 TW facility and to carry out several experimental campaigns abroad.The first part of the work aims at improving the reliability of ion beams through the precise positioning of solid targets used in laser-driven ion acceleration. For this purpose, a Target Positioning Interferometer (TPI) that reaches subwavelength positioning precision was developed. The TPI’s novel design is a modified Michelson interferometer that incorporates an aspherical converging lens in the target arm to transform it from a relative to an absolute positioning device, having a single unambiguity point in space. The high positioning accuracy is also achieved by a numerical fringe analysis algorithm that maximizes the extraction of signals with high signal-to-noise ratio, in an optimized timeframe. The development of a fast algorithm is crucial to make the TPI a viable solution for its implementation in a laser-based ion accelerator.The second part of the work is focused on enhancing the acceleration mechanism to generate higher ion numbers and kinetic energies, leading to more intense ion bunches. The solid targets used are typically flat metallic targets which allow for less than 10% of laser energy absorption, thereby limiting the laser-to-ion conversion efficiency to a few percent. A way to increase this conversion efficiency is by using target surface nanostructuration to trap the incoming laser pulse, ultimately leading to a greater energy transfer to the ions. We have shown, both theoretically and experimentally, that a careful optimization of a nanostructure’s geometrical parameters, in particular for nanospheres and nanowires, leads to multiple-fold enhancements of ion numbers and kinetic energies, compared to the use of the same laser pulse incident on flat targets of the same material.The final part of the work is dedicated to the development of efficient particle diagnostics suitable for being implemented on high repetition-rate laser-based ion beamlines. We first performed the absolute number calibration of the new EBT-XD type of radiochromic films (RCF). The EBT-XD exhibit larger dose detection range and higher minimum energy threshold compared to their EBT3 counterpart, hence more suitable for intense ion beamlines. A severe response quenching was remarked when the Bragg peak of the measured particle falls directly within the active layer of the RCF, causing significant particle number misestimation errors. Finally, we have developed a Thomson Parabola (TP) and Time-of-Flight cross-calibrated set of particle diagnostics that were incorporated on the ALLS 100 TW ion beamline. The TP spectrometer uses a microchannel plate (MCP) detector that was calibrated from single proton impacts to reconstruct the response function of the MCP detection system
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Metzkes, Josefine. "Studying the interaction of ultrashort, intense laser pulses with solid targets." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-201735.
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This thesis experimentally investigates laser-driven proton acceleration in the regime of target normal sheath acceleration (TNSA) using ultrashort (pulse duration τL = 30 fs), high power (∼100TW) laser pulses. The work focuses on how the temporal intensity profile of the ultrashort laser pulse influences the plasma formation during the laser-target interaction and the subsequent acceleration process. The corresponding experiments are performed at the Draco laser facility at the Helmholtz-Zentrum Dresden – Rossendorf.
The main result of the thesis is the experimental observation of transverse spatial modulations in the laser-driven proton distribution. The onset of the modulations occurs above a target-dependent laser energy threshold and is found to correlate with parasitic laser emission preceding the ultrashort laser pulse.
The analysis of the underlying plasma dynamics by using numerical simulations indicates that plasma instabilities lead to the filamentation of the laser-accelerated electron distribution. The resulting spatial pattern in the electron distribution is then transferred to the proton distribution during the acceleration process. The plasma instabilities, which the electron current is subjected to, are a surface-ripple-seeded Rayleigh-Taylor or a Weibel instability.
Regarding their occurrence, both instabilities show a strong dependence on the initial plasma conditions at the target. This supports the experimentally observed connection between the temporal intensity profile of the laser pulse and the development of spatial modulations in the proton distribution.
The study is considered the first observation of (regular) proton beam modulations for TNSA in the regime of ultrashort laser pulses and micrometer thick target foils. The experiments emphasize the requirement for TNSA laser power scaling studies under the consideration of realistic laser-plasma interaction conditions. In that way, the potential of the upcoming generation of Petawatt power lasers for laser-driven proton acceleration can be assessed and fully exploited.
In the second part of the thesis, experimental pump-probe techniques are investigated. With an imaging method termed high depth-of-field time-resolved microscopy in a reflective probing setup, micrometer-size local features of the near-critical density plasma as well as the global topography of the plasma can be resolved. The spatio-temporal resolution of the target ionization and heating dynamics is achieved by probing the target reflectivity, whereas the angular distribution of the reflected probe beam carries signatures of the plasma expansion. The presented probing technique avails to correlate the temporal intensity profile of a laser pulse with the spatio-temporal plasma evolution triggered upon laser-target interaction.
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Kluge, Thomas. "Enhanced Laser Ion Acceleration from Solids." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-102681.
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This thesis presents results on the theoretical description of ion acceleration using ultra-short ultra-intense laser pulses. It consists of two parts. One deals with the very general and underlying description and theoretic modeling of the laser interaction with the plasma, the other part presents three approaches of optimizing the ion acceleration by target geometry improvements using the results of the first part. In the first part, a novel approach of modeling the electron average energy of an over-critical plasma that is irradiated by a few tens of femtoseconds laser pulse with relativistic intensity is introduced.
The first step is the derivation of a general expression of the distribution of accelerated electrons in the laboratory time frame. As is shown, the distribution is homogeneous in the proper time of the accelerated electrons, provided they are at rest and distributed uniformly initially. The average hot electron energy can then be derived in a second step from a weighted average of the single electron energy evolution. This result is applied exemplary for the two important cases of infinite laser contrast and square laser temporal profile, and the case of an experimentally more realistic case of a laser pulse with a temporal profile sufficient to produce a preplasma profile with a scale length of a few hundred nanometers prior to the laser pulse peak. The thus derived electron temperatures are in excellent agreement with recent measurements and simulations, and in particular provide an analytic explanation for the reduced temperatures seen both in experiments and simulations compared to the widely used ponderomotive energy scaling.
The implications of this new electron temperature scaling on the ion acceleration, i.e. the maximum proton energy, are then briefly studied in the frame of an isothermal 1D expansion model. Based on this model, two distinct regions of laser pulse duration are identified with respect to the maximum energy scaling. For short laser pulses, compared to a reference time, the maximum ion energy is found to scale linearly with the laser intensity for a simple flat foil, and the most important other parameter is the laser absorption efficiency. In particular the electron temperature is of minor importance. For long laser pulse durations the maximum ion energy scales only proportional to the square root of the laser peak intensity and the electron temperature has a large impact. Consequently, improvements of the ion acceleration beyond the simple flat foil target maximum energies should focus on the increase of the laser absorption in the first case and the increase of the hot electron temperature in the latter case.
In the second part, exemplary geometric designs are studied by means of simulations and analytic discussions with respect to their capability for an improvement of the laser absorption efficiency and temperature increase. First, a stack of several foils spaced by a few hundred nanometers is proposed and it is shown that the laser energy absorption for short pulses and therefore the maximum proton energy can be significantly increased. Secondly, mass limited targets, i.e. thin foils with a finite lateral extension, are studied with respect to the increase of the hot electron temperature. An analytical model is provided predicting this temperature based on the lateral foil width. Finally, the important case of bent foils with attached flat top is analyzed. This target geometry resembles hollow cone targets with flat top attached to the tip, as were used in a recent experiment producing world record proton energies. The presented analysis explains the observed increase in proton energy with a new electron acceleration mechanism, the direct acceleration of surface confined electrons by the laser light. This mechanism occurs when the laser is aligned tangentially to the curved cone wall and the laser phase co-moves with the energetic electrons. The resulting electron average energy can exceed the energies from normal or oblique laser incidence by several times. Proton energies are therefore also greatly increased and show a theoretical scaling proportional to the laser intensity, even for long laser pulses.
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Sinigardi, Stefano <1985>. "Laser driven proton acceleration and beam shaping." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6230/.
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In the race to obtain protons with higher energies, using more compact systems at the same time, laser-driven plasma accelerators are becoming an interesting possibility. But for now, only beams with extremely broad energy spectra and high divergence have been produced.
The driving line of this PhD thesis was the study and design of a compact system to extract a high quality beam out of the initial bunch of protons produced by the interaction of a laser pulse with a thin solid target, using experimentally reliable technologies in order to be able to test such a system as soon as possible.
In this thesis, different transport lines are analyzed. The first is based on a high field pulsed solenoid, some collimators and, for perfect filtering and post-acceleration, a high field high frequency compact linear accelerator, originally designed to accelerate a 30 MeV beam extracted from a cyclotron.
The second one is based on a quadruplet of permanent magnetic quadrupoles: thanks to its greater simplicity and reliability, it has great interest for experiments, but the effectiveness is lower than the one based on the solenoid; in fact, the final beam intensity drops by an order of magnitude.
An additional sensible decrease in intensity is verified in the third case, where the energy selection is achieved using a chicane, because of its very low efficiency for off-axis protons.
The proposed schemes have all been analyzed with 3D simulations and all the significant results are presented. Future experimental work based on the outcome of this thesis can be planned and is being discussed now.
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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.
Full textAbstract:
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.
18
Jung, Daniel. "Ion acceleration from relativistic laser nano-target interaction." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-140744.
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Jäckel, Oliver. "Characterisation of ion acceleration with relativistic laser-plasmas." Tönning Lübeck Marburg Der Andere Verl, 2009. http://d-nb.info/995862729/04.
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Abuazoum, Salima. "Experimental study of laser-driven electron and proton acceleration." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18698.
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Lécz, Zsolt. "Laser ion acceleration from a double-layer metal foil." Phd thesis, TU Darmstadt, 2013. https://tuprints.ulb.tu-darmstadt.de/3335/1/PHD_final.pdf.
Full textAbstract:
The laser-ion acceleration with ultra-intense and ultra-short laser pulses has opened a
new field of accelerator physics over the last decade. Fast development in laser systems are
capable of delivering short pulses of a duration of a few hundred femtoseconds at intensities
between 10^18-10^20 W/cm2. At these high intensities the laser-matter interaction induces
strong charge separation, which leads to electric fields exceeding the acceleration gradients
of conventional devices by 6 orders of magnitude. The particle dynamics and energy
absorption of the laser pulse can be understood by means of high-performance simulation
tools.
In the framework of the LIGHT (Laser Ion Generation, Handling and Transport) project
our goal is to provide an analytical description of the 3D distribution of the protons accelerated
via TNSA (Target Normal Sheath Acceleration). In this acceleration mechanism
the short pulse impinging on a metal foil heats the electrons to relativistic energies, which
triggers the strong charge separation field on the opposite target surface (Debye-sheath).
The accelerated light ions (proton, carbon, oxygen) observed in the experiments originate
from the contamination layer deposited on the surface. The thickness of this layer in the
experiments is not known exactly. According to our study these ions can be accelerated in
three different regimes depending on layer thickness: quasi-static acceleration (QSA, for
thin layers), plasma expansion (for thick layers) and a not well understood intermediate
(or combined) regime.
In a laser-plasma simulations time-dependent hot electron density and temperature are
observed, therefore we performed plasma simulations with a well defined and constant
initial hot electron distribution. Thus the simulation results are easier to compare with
analytical models. In our case the theoretical investigation of the TNSA involves the
understanding of the charge separation effects at the surface of a two-temperature plasma
and the consequent proton acceleration in one dimension. We omit the detailed dynamics
of the laser-plasma interaction by assuming a preheated electron distribution. With our 1D
electrostatic simulations we investigate the influence of the proton layer thickness on the
TNSA energy spectrum. Additionally we investigate the divergence of the protons using
2D simulations: In these we simulate the heating of the electrons by the laser pulse.
Numerical studies in this work were carried out using a Particle-in-Cell (PIC) plasma
simulation code (VORPAL). The target is defined as a single-ionized plasma with a doublelayer
structure: a bulk layer of heavy ions, which represents the metal foil itself and a much
thinner proton layer, which serves as the contamination layer. The layer is considered thin
if it is thinner compared to the skin depth of the accelerating electric field. For a thin
proton layer the quasi-static acceleration is the governing mechanism. When the proton
layer is larger than skin depth the process can be described as plasma expansion.
I found that the energy and phase-space distribution of the protons strongly depends
on the layer thickness. In the QSA regime the proton spectrum shows a nearly monoenergetic
feature, but the maximum energy is typically low compared to the plasma expansion regime, where the protons have a broad exponential energy spectrum. For the
plasma expansion we observe a cut-off energy that logarithmically depends on the acceleration
time.
The simulation results in these two extreme cases for one- and two-temperature plasmas
have been extensively compared to analytical predictions showing an overall good
agreement. In the intermediate regime an analytical expression could be obtained for the
energy conversion from electrons to protons as a function of electron parameters and layer
thickness. By changing the layer thickness a smooth transition between the two extreme
cases could be identified.
The proton layer thickness also has an impact on the transversal acceleration, which
defines the divergence of a proton beam. In the two-dimensional TNSA simulations a laser
pulse is needed to generate the hot electron population in the plasma. The simulations show
that theoretically with the right laser pulse duration and layer thickness the divergence
of the most energetic protons can be reduced almost to zero. In the QSA regime the
transversal distribution and temperature of the hot electrons changes too quickly compared
to the time-scale of the acceleration. The analytical treatment of the divergence is only
possible for the thick layers, where the plasma expansion model is suitable to describe the
physics. The model derived in this work can be used to reconstruct the whole velocity
phase-space of the protons in 3D. Therefore it enables us to perform particle tracking and
beam optics simulations with realistic TSNA proton bunch. The envelope angle of the
protons measured in experiments can be also reproduced using our 2D model.
The beam quality during motion through magnetic focusing and energy selection systems
downstream of the laser acceleration is sensitive to the initial distribution. After
benchmarking our analytic models, simulation results and measurements with each another,
we are confident we can now provide sufficiently realistic particle distributions to be
expected a few mm from the target in TNSA. Using our particle distributions as input, the
effect of co-moving electrons, the degradation of the transverse emittance and chromatic
aberration effects can be investigated. Thereby this study hopefully contributes to the goal
of the Light project: Coupling the new laser ion acceleration techniques to conventional
accelerator facilities.
22
Popp, Antonia. "Dynamics of electron-acceleration in laser-driven wakefields: Acceleration limits and asymmetric plasma waves." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-138159.
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Doche, Antoine. "Particle acceleration with beam driven wakefield." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX023/document.
Full textAbstract:
Les accélérateurs par onde de sillage plasma produites par faisceaux de particules (PWFA) ou par faisceaux laser (LWFA) appartiennent à un nouveau type d’accélérateurs de particules particulièrement prometteur. Ils permettent d’exploiter des champs accélérateurs jusqu’à cent Gigaélectronvolt par mètre alors que les dispositifs conventionnels se limitent à cent Megaélectronvolt par mètre. Dans le schéma d’accélération par onde de sillage plasma, ou par onde de sillage laser, un faisceau de particules ou une impulsion laser se propage dans un plasma et créé une structure accélératrice dans son sillage : c’est une onde de densité électronique à laquelle sont associés des champs électromagnétiques dans le plasma. L’un des principaux résultats de cette thèse a été la démonstration de l’accélération par onde de sillage plasma d’un paquet distinct de positrons. Dans le schéma utilisé, un plasma de Lithium était créé dans un four, et une onde plasma était excitée par un premier paquet de positrons (le drive ou faisceau excitateur) et l’énergie était extraite par un second faisceau (le trailing ou faisceau témoin). Un champ accélérateur de 1,36 GeV/m a ainsi été obtenu durant l’expérience, pour une charge accélérée typique de 40 pC. Nous montrons également ici la possibilité d’utiliser différents régimes d’accélération qui semblent très prometteurs. Par ailleurs, l’accélération de particule par sillage laser permet quant à elle, en partant d’une impulsion laser femtoseconde de produire un faisceau d’électron quasi-monoénergétique d’énergie typique de l’ordre de 200 MeV. Nous présentons les résultats d’une campagne expérimentale d’association de ce schéma d’accélération par sillage laser avec un schéma d’accélération par sillage plasma. Au cours de cette expérience un faisceau d’électrons créé par laser est refocalisé lors d’une interaction dans un second plasma. Une étude des phénomènes associés à cette plateforme hybride LWFA-PWFA est également présentée. Enfin, le schéma hybride LWFA-PWFA est prometteur pour optimiser l’émission de rayonnement X par les électrons du faisceau de particule crée dans l’étage LWFA de la plateforme. Nous présentons dans un dernier temps la première réalisation expérimentale d’un tel schéma et ses résultats prometteursPlasma wakefield accelerators (PWFA) or laser wakefield accelerators (LWFA) are new technologies of particle accelerators that are particularly promising, as they can provide accelerating fields of hundreds of Gigaelectronvolts per meter while conventional facilities are limited to hundreds of Megaelectronvolts per meter. In the Plasma Wakefield Acceleration scheme (PWFA) and the Laser Wakefield Acceleration scheme (LWFA), a bunch of particles or a laser pulse propagates in a gas, creating an accelerating structure in its wake: an electron density wake associated to electromagnetic fields in the plasma. The main achievement of this thesis is the very first demonstration and experimental study in 2016 of the Plasma Wakefield Acceleration of a distinct positron bunch. In the scheme considered in the experiment, a lithium plasma was created in an oven, and a plasma density wave was excited inside it by a first bunch of positrons (the drive bunch) while the energy deposited in the plasma was extracted by a second bunch (the trailing bunch). An accelerating field of 1.36 GeV/m was reached during the experiment, for a typical accelerated charge of 40 pC. In the present manuscript is also reported the feasibility of several regimes of acceleration, which opens promising prospects for plasma wakefield accelerator staging and future colliders. Furthermore, this thesis also reports the progresses made regarding a new scheme: the use of a LWFA-produced electron beam to drive plasma waves in a gas jet. In this second experimental study, an electron beam created by laser-plasma interaction is refocused by particle bunch-plasma interaction in a second gas jet. A study of the physical phenomena associated to this hybrid LWFA-PWFA platform is reported. Last, the hybrid LWFA-PWFA scheme is also promising in order to enhance the X-ray emission by the LWFA electron beam produced in the first stage of the platform. In the last chapter of this thesis is reported the first experimental realization of this last scheme, and its promising results are discussed
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Hanton, Fiona. "Laser ion acceleration from ultrathin foils and application to radiobiology." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.706690.
Full textAbstract:
Laser driven ion sources offer a potential alternative to conventional ion accelerators currently used in hadrontherapy for cancer treatment. The unique characteristics of the ion beams sets the basis for development toward therapeutic use. The work presented in this thesis seeks to overcome the present limitations of laser-driven ion accelerators and to demonstrate the ion beam parameters required to make this a viable treatment option. Ultra-thin copper and gold foil targets were irradiated with intense laser pulses at normal incidence by varying laser and target parameters. For copper, the peak ion energies were observed to quadratically scale with the dimensionless fluence parameter, suggesting efficient Radiation Pressure Acceleration in the Light Sail phase in a hybrid acceleration regime. For gold targets, the production of high peak ion energies of ~20 MeV, ~12 MeV/nucleon and 7.5 MeV/nucleon for H+, C6+ and Au45+ were observed, respectively. In particular, the Au45+ ion energies translate to approximately 1.5-2 GeV per Au ion (for energies exceeding and including the spectral peak). 2D PIC simulations were performed and were found to be in agreement with experimentally observed data. The radiobiological work focused on studying DNA Double Strand Breaks (DSBs) following the irradiation of AG01522 cells with proton and carbon ions at ultra-high dose rates of ≥10A˄9 Gys˄-1. This was done by quantitatively measuring the dispersion of 53BP1 foci over a 24 hour period for cells irradiated with 10 MeV (5 keV/μm) protons and 5 MeV/nucleon (310 keV/μm) carbon ions. The slow repair kinetics and large number of foci remaining at 24 hours from carbon ion irradiation was indicative of more severe DSBs compared to the lower LET exposure from protons. The relative biological effectiveness for protons and carbon ions were found to be RBE_1H = 1.6 ± 0.2 and RBE_12C = 13 ± 9.
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Sgattoni, Andrea <1982>. "Theoretical and numerical study of the laser-plasma ion acceleration." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3811/.
Full textAbstract:
The laser driven ion acceleration is a burgeoning field of resarch
and is attracting a growing number of scientists since the first results reported in 2000 obtained
irradiating thin solid foils by high power laser pulses.
The growing interest is driven by the peculiar characteristics of the produced bunches,
the compactness of the whole accelerating system and the very short
accelerating length of this all-optical accelerators.
A fervent theoretical and experimental work has been done since then.
An important part of the theoretical study is done by means of numerical simulations and the most widely used
technique exploits PIC codes (“Particle In Cell'”).
In this thesis the PIC code AlaDyn, developed by our research group considering innovative
algorithms, is described. My work
has been devoted to the developement of the code and
the investigation of the laser driven ion acceleration
for different target configurations.
Two target configurations for the proton acceleration are
presented together with the results of the 2D and 3D numerical investigation.
One target configuration consists of a solid foil with a low density layer attached on the
irradiated side. The nearly critical plasma of the foam layer allows a very
high energy absorption by the target and an increase of the proton
energy up to a factor 3, when compared to the ``pure'' TNSA configuration.
The differences of the regime with respect to the standard TNSA are described
The case of nearly critical density targets has been investigated with
3D simulations. In this case the laser travels throughout the plasma
and exits on the rear side. During the propagation, the laser drills a channel
and induce a magnetic vortex that expanding on the rear side of the targer is source of a
very intense electric field. The protons of the plasma are
strongly accelerated up to energies of 100 MeV using a 200PW laser.
26
Zeil, Karl. "Efficient laser-driven proton acceleration in the ultra-short pulse regime." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-117484.
Full textAbstract:
The work described in this thesis is concerned with the experimental investigation of the acceleration of high energy proton pulses generated by relativistic laser-plasma interaction and their application. Using the high intensity 150 TW Ti:sapphire based ultra-short pulse laser Draco, a laser-driven proton source was set up and characterized. Conducting experiments on the basis of the established target normal sheath acceleration (TNSA) process, proton energies of up to 20 MeV were obtained. The reliable performance of the proton source was demonstrated in the first direct and dose controlled comparison of the radiobiological effectiveness of intense proton pulses with that of conventionally generated continuous proton beams for the irradiation of in vitro tumour cells. As potential application radiation therapy calls for proton energies exceeding 200 MeV. Therefore the scaling of the maximum proton energy with laser power was investigated and observed to be near-linear for the case of ultra-short laser pulses. This result is attributed to the efficient predominantly quasi-static acceleration in the short acceleration period close to the target rear surface. This assumption is furthermore confirmed by the observation of prominent non-target-normal emission of energetic protons reflecting an asymmetry in the field distribution of promptly accelerated electrons generated by using oblique laser incidence or angularly chirped laser pulses. Supported by numerical simulations, this novel diagnostic reveals the relevance of the initial prethermal phase of the acceleration process preceding the thermal plasma sheath expansion of TNSA. During the plasma expansion phase, the efficiency of the proton acceleration can be improved using so called reduced mass targets (RMT). By confining the lateral target size which avoids the dilution of the expanding sheath and thus increases the strength of the accelerating sheath fields a significant increase of the proton energy and the proton yield was observed.
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Willingale, Louise. "Ion acceleration from high intensity laser plasma interactions : measurements and applications." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504795.
Full textAbstract:
This thesis presents measurements of high energy ion beams accelerated from high intensity laser interactions, with underdense through to near critical density plasmas, and also presents an application of laser generated ion beams. The first experimental measurements of longitudinally accelerated ion beams from high intensity (-1020 Wcm-2 ) laser interactions with an underdense (0.04 ne) helium plasma are presented. The ion beam was found to have a maximum energy for He2+ of 40+3 _8 MeV, with the highest energy ions being collimated to a cone of less than 10ø. Two dimensional particle-in-cell simulations show that additional effects, due to the time varying magnetic field associated with the fast electron current, enhance the accelerating electric field and provides a focusing mechanism on the ions. Very low density foam targets were used to investigate proton acceleration from near to critical density plasmas. Experimental results show a decrease in acceleration efficiency just above the critical density. Simulations of the interactions show the proton acceleration is very sensitive to the ability of the laser to propagate through the plasma. The lowest density foams allow the best laser propagation, thus enabling proton beams to be accelerated to energy and numbers comparable to those from a solid target. The suitability of a laser generated proton beam for the measurement of self-generated magnetic fields in laser generated plasma has been investigated. The technique was then used to study a novel magnetic reconnection geometry lIsing two laser beams. Proton probing provides evidence for the formation of the reconnection layer and the corresponding instabilities.
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Kreuzer, Christian [Verfasser], and Jörg [Akademischer Betreuer] Schreiber. "Technological developments for Laser Ion Acceleration / Christian Kreuzer ; Betreuer: Jörg Schreiber." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/116353420X/34.
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Ettlinger, Oliver. "Studies of near-critical density laser plasma interactions for ion acceleration." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/58099.
Full textAbstract:
This thesis presents experimental research, complemented by numerical particle-in-cell simulations, studying the interaction of a high power CO2 laser with near-critical density plasmas. The experiments all occurred around relativistic intensities, a0 ≃ 1, where radiation pressure effects are important. Experiments with a high intensity, 3.5 ps beam with peak intensities IL > 1016 Wcm−2, focussed on to a shaped, over-critical density hydrogen gas target were studied. The accelerated proton beams showed spectral peaking, indicative of radiation pressure or collisionless shock driven acceleration. Higher than previously observed proton energies for this laser system were observed, with peak energies > 1.8 MeV, and energy spreads as low as ∼ 5%. The peak proton energy showed good agreement with the predicted energy scaling for hole-boring RPA, with Ep ∝ IL/ni. Experiments were also conducted at lower intensities, with a 5 ps beam of peak intensity IL∼ 1015 Wcm−2 again focussed on to a shaped hydrogen gas target. Here, the unique laser and target conditions lead to a plasma grating structure being formed in the density ramp preceding the critical surface, from which radiation pressure driven acceleration could occur. The limited mass of these grating structures, along with the suppressed background density, results in enhanced acceleration when compared to that at the unmodified critical surface. Experimentally, a dependence on the peak proton energy compared with the scale length of the plasma preceding the critical surface was observed, attributed to an optimal density profile for the grating formation. Finally, using the same experimental conditions, an alternative method for producing thin gas targets was explored, through two colliding blast waves. Proton acceleration was studied for relative levels of separation between the shock fronts, with the optimal case being at the point of collision. Numerical simulations suggest that acceleration was again enhanced by the creation of grating structures in the sharpened density profile.
30
Higginson, Adam. "Optimisation and control of ion acceleration in intense laser-foil interactions." Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30649.
Full textAbstract:
This thesis reports on experimental and numerical investigations of ion acceleration driven by the interaction of short, ultra-intense (> 1020 Wcm-2), linearly polarised pulses of laser light with thin foil targets. Four investigations were performed to explore various aspects of the acceleration and the physics underpinning potential applications of these sources. The first investigation explores a hybrid scheme of radiation pressure-sheath acceleration, enhanced by relativistic transparency at an optimum foil thickness. Efficient proton acceleration with energies exceeding 94 MeV is achieved. The range of parameters over which this hybrid scenario occurs is discussed, and implications for ion acceleration driven by next-generation, multi-PW laser facilities are explored. The second investigation concerns the diagnosis of the highly transient electric field responsible for ion acceleration in the target normal sheath acceleration (TNSA) regime. High resolution, temporally-resolved measurements of the field evolution are obtained using proton deectometry. In the third investigation, a laser generated proton beam is used to heat and preexpand the rear-surface of a secondary foil. This target is then irradiated by a second laser pulse, with the resultant proton beam spatial-intensity distribution measured. For an increasingly expanded target the maximum proton energy, overall number of accelerated protons and the size of the proton beam consistently decreases. A simple analytical model describing the expansion behaviour is developed. In the final investigation, initial steps towards proton focusing for the purposes of proton fast ignition (PFI) using novel conical targets are addressed. Clear focusing is observed for an open-tipped conical target. These beams are used to isochorically heat copper, with the X-ray emission imaged. Finally, in order to close in on a realistic PFI scenario, the effects of an external plasma surrounding the cone is explored.
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Morrison, John T. "Selective Deuteron Acceleration using Target Normal Sheath Acceleration." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1365523293.
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Wong, Liang Jie. "Compact laser-driven electron acceleration, bunch compression and coherent nonlinear Thomson scattering." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84900.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 189-195).
Coherent hard x-rays have many medical, commercial and academic research applications. To facilitate the design of a table-top coherent hard x-ray source, this thesis studies the linear acceleration of electrons by optical lasers in unbounded vacuum, the linear acceleration and compression of electron bunches by coherent terahertz pulses in cylindrical waveguides, and the generation of coherent hard x-ray radiation by nonlinear Thomson scattering of compressed electron bunches. The Lawson-Woodward theorem describes conditions prohibiting net electron acceleration in laser-electron interactions. We point out how the Lawson-Woodward theorem permits net linear acceleration of a relativistic electron in unbounded vacuum and verify this with electrodynamic simulations. By hypothesizing that substantial net linear acceleration is contingent on the field's ability to bring the particle to a relativistic energy in its initial rest frame, we derive a general formula for the acceleration threshold, which is useful as a practical guide to the laser intensities that linear vacuum acceleration requires. We characterize the scaling laws of linear acceleration by a pulsed radially-polarized beam in infinite vacuum, showing that greater energy gain is achievable with tighter focusing and the use of pre-accelerated electrons. We propose a two-color linear acceleration scheme that exploits changes in the interference pattern caused by the Gouy phase shift to achieve over 90% the one-color theoretical gain limit, more than twice the 40% achievable with a one-color paraxial beam. Interested in capitalizing on the larger wavelengths of coherent terahertz radiation to accelerate larger electron bunches, we study electron acceleration and bunch compression in a cylindrical metal-coated dielectric waveguide. We numerically predict an achievable acceleration gradient of about 450 MeV/m using a 20 mJ terahertz pulse, and separately achieve a 50 times compression to a few-femtosecond duration of a 1.6 pC relativistic electron bunch. Finally, we numerically study the production of coherent hard x-rays via nonlinear Thomson scattering for different degrees of laser focusing. We derive an approximate analytical formula for the optimal incident field intensity that maximizes the radiation intensity spectral peak for a given output and input frequency.
by Liang Jie Wong.
Ph.D.
33
Schmid, Karl. "Supersonic Micro-Jets And Their Application to Few-Cycle Laser-Driven Electron Acceleration." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-104632.
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Ju, Jinchuan. "Electron acceleration and betatron radiation driven by laser wakefield inside dielectric capillary tubes." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00861267.
Full textAbstract:
This dissertation addresses electron acceleration and the associated betatron X-ray radiation generated by laser wakefield inside dielectric capillary tubes. Focusing the state-of-the-art multi-terawatt laser pulses, high peak intensity, of the order of 1018 W/cm2, can be achieved in the focal plane, where a plasma bubble free of electron is formed just behind the laser. Owing to space charge separation ultrahigh electric fields, of the order of 100 GV/m, occur inside the plasma bubble, providing the possibility to accelerate electrons up to GeV-class over merely a centimetre-scale distance. Furthermore, ultra-short synchrotron-like X-ray radiation, known as betatron radiation, is produced simultaneously when the accelerated electrons are transversely wiggled by the radial electric field inside the plasma bubble. This thesis reports experimental results on the generation and optimization of electron and X-ray beams, particularly when a capillary tube is used to collect the energy of laser halos in the focal plane to facilitate the laser keeping self-focused over a long distance. Employing the 40 fs, 16 TW Ti:sapphire laser at the Lund Laser Centre (LLC) in Sweden, either peaked or widely-spread accelerated electron spectra with a typical beam charge of tens of pC were measured with a maximum energy up to 300 MeV in 10 mm long capillary tubes. Meanwhile, betatron X-ray radiation consisting of 1-10 keV photons was measured with a peak brightness of the order of 1021 photons/s/mm2/mrad2/0.1%BW, which is around 30 times higher than that in the case of a 2 mm gas jet without external optical guiding. When the laser pointing fluctuation is compensated, exceptionally reproducible electron beams are obtained with fluctuations of only 1 mrad RMS in beam pointing, a few percent in electron energy, and around 20% RMS in beam charge. The relatively large instability of beam charge is found to be essentially correlated to laser power fluctuation. Moreover, betatron radiation is able to provide the diagnostics about electron acceleration process and average number of betatron oscillations fulfilled by electrons inside the plasma bubble. The typical X-ray source size (waist of Gaussian distribution at 1/e2 intensity) is quantified to be ~2.5 μm using Fresnel diffraction induced by a razor blade, which furthermore yields the corresponding normalized RMS emittance of electron beam 0.83π mm mrad. Three dimensional particle-in-cell (PIC) modelings are in good agreement with the experimental findings. The PIC simulations also reveal the generated electron bunches (or X-ray bursts) have pulse durations as short as 10 fs.
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Foster, Peta Suzanne. "Characterisation of plasma mirror activation and laser-driven ion studies." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676468.
Full textAbstract:
In this thesis, a body of work is presented which contributes towards the improved understanding of plasma mirror operation and in 'particular, the switch-on dynamics and picosecond timescale reflectivity. Degradation in the performance of the baseline anti-reflective properties of the plasma mirrors is observed 1.5 picoseconds prior to the main pulse peak. This is believed to be the first observation of this effect. The rise time of these plasma optics is measured in a simple numerical model constructed to elucidate the underlying physics. The ultimate aim is to reveal the underlying dynamics so as to be able to ascertain how to best operate these optics to achieve ultra-high contrast. This would benefit high-intensity interactions, potentially enhancing laser-driven ion acceleration and high harmonic production. This thesis also explores the use of these enhanced-contrast pulses in laser-driven ion acceleration studies, at the cutting edge of both on-target intensity and ultra-thin foil thickness. Continuous wave laser heating of skin depth foils is investigated for the purpose of contaminant removal and target thinning. In addition, ultra-high intensity interactions were explored, where it was hoped the dynamics might indicate a transition to a new and more efficient acceleration regime, namely radiation pressure acceleration. Both of these ion studies have a key signature of higher peak ion energies, and although the energy range of ions was not increased as far as had been hoped, the thesis endeavors to shed light on the current observations and highlight limitations encountered, such as to inform the ongoing research moving forward.
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Zakharov, Venjamin E., and Claudia-Veronika Meister. "Acceleration and heating in the auroral magnetosphere by current driven electrostatic ion cyclotron turbulence." Universität Potsdam, 2000. http://opus.kobv.de/ubp/volltexte/2007/1495/.
Full textAbstract:
A numerical MHD model is developed to investigate acceleration and heating of both thermal and auroral plasma. This is done for magnetospheric flux tubes in which intensive field aligned currents flow. To give each of these tubes, the empirical Tsyganenko model of the magnetospheric field is used. The parameters of the background plasma outside the flux tube as well as the strength of
the electric field of magnetospheric convection are given. Performing the numerical calculations, the distributions of the plasma densities, velocities, temperatures, parallel electric field and current, and of the coefficients of thermal conductivity are obtained in a self-consistent way. It is found that EIC turbulence develops effectively in the thermal plasma. The parallel electric field develops under the action of the anomalous resistivity. This electric field accelerates both the thermal and the auroral plasma. The thermal turbulent plasma is also subjected to an intensive heating. The increase of the plasma of the Earth's ionosphere. Besides, studying the growth and dispersion properties of oblique ion cyclotron waves excited in a drifting magnetized plasma, it is shown that under non-stationary conditions such waves may reveal the properties of bursts of polarized transverse electromagnetic waves at frequencies near the patron gyrofrequency.
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Böker, Jürgen [Verfasser], Oswald [Akademischer Betreuer] Willi, and Carsten [Akademischer Betreuer] Müller. "Laser-Driven Proton Acceleration with Two Ultrashort Laser Pulses / Jürgen Böker. Gutachter: Carsten Müller. Betreuer: Oswald Willi." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2015. http://d-nb.info/1072500612/34.
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Popp, Antonia [Verfasser], and Stefan [Akademischer Betreuer] Karsch. "Dynamics of electron-acceleration in laser-driven wakefields : acceleration limits and asymmetric plasma waves / Antonia Popp. Betreuer: Stefan Karsch." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://d-nb.info/1018616284/34.
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Jung, Daniel [Verfasser], and Dietrich [Akademischer Betreuer] Habs. "Ion acceleration from relativistic laser nano-target interaction / Daniel Jung. Betreuer: Dietrich Habs." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1020790369/34.
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Scott, Graeme Gordon. "On the use of multiple high intensity laser pulses in ion acceleration experiments." Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25468.
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Compact laser driven ion sources have inspired cautious optimism that they may provide an alternative to conventional accelerators for existing applications, such as in medicine, or aid the realisation of new ones such as fusion energy. However, the sources must be developed, with increased conversion efficiency of laser to proton energy being high on the list of requirements. Recent reports in the literature have shown that record conversion efficiencies can be achieved with double pulse interactions, and this thesis proceeds with this theme. The double pulse operation of the plasma mirror is characterised for the first time, in terms of the post interaction far field quality, and integrated reflectivity. The main pulse reflectivity is significantly enhanced to 96% and the far field remains of high optical quality up to five picoseconds after the prepulse interaction, within the regime for conversion efficiency enhancement. These observations are explained by perturbations of the quasi-near field intensity distribution seeding nonuniformities in the plasma expansion of the plasma mirror surface. A novel plasma half cavity target geometry is investigated which utilises the high fraction of laser energy reflected from an ionised surface and refocuses it such that a double pulse interaction is attained. This new geometry is found to double the laser to proton energy conversion efficiency, compared with planar foil interactions and to modify the low energy region of the proton spectrum. For pulse separations of tens of picoseconds, a long time delay regime is identified for planar foil interactions, where a significant reduction in maximum proton energy and conversion efficiency is reversed, and return to that expected for single pulse interactions. This is explained by the main pulse interacting with bulk target expansion induced by the prepulse. Increased electron temperatures from enhanced absorption in the preplasma are found to mitigate the detrimental effects on ion acceleration, associated with rear surface density scale lengths.
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Zaim, Neïl. "Modeling electron acceleration driven by relativistic intensity few-cycle laser pulses on overdense plasmas." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX089.
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Nous étudions dans cette thèse théorique et numérique l'accélération d'électrons lors de l'interaction entre une impulsion laser d'intensité relativiste et un plasma surdense. Cette interaction est très sensible au profil de densité sur la face avant du plasma et deux régimes différents, correspondant à deux thématiques de recherche développées dans cette thèse, peuvent être considérés.Premièrement, pour des interfaces plasma-vide très abruptes, les mécanismes menant à l'émission d'électrons sont bien compris. Les électrons gagnent en particulier une grande quantité d'énergie lors de leur interaction dans le vide avec l'impulsion laser réfléchie. Nous proposons d'optimiser cette accélération en utilisant des faisceaux polarisés radialement, qui sont caractérisés par la présence d'un fort champ longitudinal, capable d'accélérer directement les électrons dans la direction de propagation du laser. Nous montrons que les plasmas surdenses conduisent à une accélération plus efficace que les autres méthodes existantes pour injecter des électrons dans une impulsion polarisée radialement. Ce résultat a été confirmé par des expériences effectuées récemment au CEA Saclay, au cours desquelles la possibilité d'accélérer des électrons dans la direction longitudinale, menant ce faisant à une diminution de la divergence angulaire du faisceau d'électrons, a été démontrée.Deuxièmement, pour des gradients de densité plasma plus grands, l'interaction n'est pas aussi bien comprise. Nous analysons des résultats expérimentaux obtenus récemment au LOA avec des impulsions de quelques cycles optiques et nous montrons que les électrons sont accélérés par une onde de sillage laser formée dans la partie quasi-critique du plasma. Ce processus ne se produit qu'avec des impulsions de quelques cycles optiques, en accord avec la condition de résonance, et se distingue par la rotation des ondes plasmas causée par le gradient de densitéThis theoretical and numerical thesis is devoted to electron acceleration from the interaction between a relativistic intensity laser pulse and an overdense plasma. This interaction is very sensitive to the density profile at the plasma front surface and two different regimes, which correspond to two distinct lines of research investigated in this thesis, can be considered.First, for sharp plasma-vacuum interfaces, the mechanisms responsible for electron emission are well understood. The electrons receive in particular a large energy gain from their interaction in vacuum with the reflected laser. We propose to optimize the acceleration by using radially polarized beams, which exhibit a strong longitudinal electric field that can directly accelerate electrons in the laser propagation direction. We show that overdense plasmas lead to more efficient acceleration than other existing methods for injecting electrons into a radially polarized pulse. This result was confirmed by recent experiments performed at CEA Saclay, in which electron acceleration in the longitudinal direction, leading to a decrease in the electron beam angular spread, is demonstrated.Secondly, for larger plasma gradient scale lengths, the interaction is not as well understood. We analyze recent experiments performed in this regime at LOA with few-cycle pulses and find that electrons are accelerated by a laser wakefield formed in the near-critical part of the plasma. This process can only be driven by few-cycle pulses, by virtue of the resonant condition, and is characterized by the rotation of the plasma waves induced by the density gradient
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Biloiu, Ioana A. "Laser induced fluorescence studies of ion acceleration in single and multiple species expanding plasmas." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10036.
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Thesis (Ph. D.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains xiv, 173 p. : ill. (some col). Vita. Includes abstract. Includes bibliographical references.
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Yu, Tongpu [Verfasser], Alexander [Akademischer Betreuer] Pukhov, and Karl-Heinz [Akademischer Betreuer] Spatschek. "Stable laser-driven proton acceleration in ultra-relativistic laser-plasma interaction / Tongpu Yu. Gutachter: Alexander Pukhov ; Karl-Heinz Spatschek." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2011. http://d-nb.info/101603508X/34.
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George, Kevin Mitchell. "Modifying the target normal sheath accelerated ion spectrum using micro-structured targets." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1482857706862922.
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Gustas, Dominykas. "High-repetition-rate relativistic electron acceleration in plasma wakefields driven by few-cycle laser pulses." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX118/document.
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Le progrès continu de la technologie laser a récemment permis l’avancement spectaculaire d’accélérateurs de particules par onde de sillage. Cette technique permet la génération de champs électriques très forts, pouvant dépasser de trois ordres de grandeurs ceux présents dans les accélérateurs conventionnels. L’accélération résultante a lieu sur une distance très courte, par conséquent les effets de la charge d’espace et de la dispersion de vitesse sont considérablement réduits. Les paquets de particules ainsi générés peuvent alors atteindre des durées de l’ordre de la femtoseconde, qui en fait un outil prometteur pour la réalisation d’expériences de diffraction ultra-rapide avec une résolution inégalée de l’ordre de quelques femtosecondes. La génération de tels paquets d’électrons avec des lasers de 1 J et d’une durée de 30 fs est à présent bien établie. Ces paramètres permettent de produire des faisceaux d’électrons de quelques centaines de MeV, et sont donc inadaptés aux expériences de diffraction. De plus, le taux de répétition de ces lasers de haute puissance est limité à quelques Hz, ce qui est insuffisant pour des expériences exigeant une bonne statistique de mesure. Notre groupe a utilisé un laser de pointe développé au laboratoire par le groupe PCO générant des impulsions de quelques millijoules, d’une durée de 3.4 fs - à peine 1.3 cycle optique - à une cadence de 1 kHz, pour accélérer des électrons par onde de sillage. Ce travail de thèse présente d’une part la première démonstration d’un accélérateur des particules relativistes opéré dans le régime de la bulle à haute cadence. L’utilisation de buses microscopiques a permis l’obtention de charges de dizaines de pC par tir. De plus, cette thèse vise à l’élargissement de notre compréhension des lois d’échelle d’accélération laser-plasma. Nous espérons que notre travail visant à la fiabilisation et l’optimisation de cette source permettra à terme de proposer un instrument accessible et fiable à la communauté scientifique, que ce soit pour la diffraction d’électrons, l’irradiation ultra-brève d’échantillons ou la génération de rayons XContinuing progress in laser technology has enabled dramatic advances in laser wakefield acceleration (LWFA), a technique that permits driving particles by electric fields three orders of magnitude higher than in conventional radio-frequency accelerators. Due to significantly reduced space charge and velocity dispersion effects, the resultant relativistic electron bunches have also been identified as a candidate tool to achieve unprecedented sub-10 fs temporal resolution in ultrafast electron diffraction (UED) experiments. High repetition rate operation is desirable to improve data collection statistics and thus washout shot-to-shot charge fluctuations inherent to plasma accelerators. It is well known that high-quality electron beams can be achieved in the blowout, or "bubble" regime, which is at present regularly accessed with ≈ 30 fs Joule-class lasers that can perform up to few shots per second. Our group on the contraryutilized a cutting edge laser system producing few-mJ pulses compressed nearly to a single optical cycle (3.4 fs) to demonstrate for the first time an MeV-grade particle accelerator with properties characteristic to the blowout regime operating at 1 kHz repetition rate. We further investigate the plasma density profile and exact laser pulse waveform effects on the source output, and show that using special gas microjets a charge of tens of pC/shot can be achieved. We expect this technique to lead to a generation of highly accessible and robust instruments for the scientific community to conduct UED experiments or to be used for other applications. This work also serves to expand our knowledge on the scalability of laser-plasma acceleration
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Cochran, Ginevra E. "New Computational and Experimental Approaches for Studying Ion Acceleration and the Intense Laser-Plasma Interaction." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534432188474908.
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Psikal, Jan. "Ion acceleration in small-size targets by ultra-intense short laser pulses (simulation and theory)." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13941/document.
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Cette thèse a pour but l'étude de l’interaction des impulsions laser brèves et ultra-intenses avec des cibles de petite taille. Nous nous intéressons surtout des phénomènes liés à l’accélération des ions aux granges énergies. L'outil principal de cette étude est notre code Particle-in-Cell (PIC) bidimensionnel, qui est capable d'effectuer le calcul du mouvement des particules et de l'évolution des champs en régime relativiste et sans collisions. Ce mémoire présente la théorie de l’accélération d’ions par laser, les simulations numériques des différents régimes d'accélération, ainsi que les algorithmes mis en œuvre dans notre code. Les nouveaux résultats obtenus dans le cadre de cette thèse concernent trois cas principaux: 1) l’interaction des impulsions laser intenses avec des cibles de la masse limitée; 2) l’accélération des protons par laser dans des gouttelettes fines d’eau vaporisé; 3) le transport latéral des électrons chauds dans une feuille mince et son effet sur l’accélération d’ions. Nos études théoriques et les simulations numériques sont appliquées pour l'interprétation des résultats des deux expériences récentes réalisées par les équipes de recherche en Allemagne et en France. Ces expériences montrent une accélération efficace d’ions dans les conditions prévues dans nos travaux théoriques. Le spectre énergétique et le nombre des protons accélérés dans les feuilles minces de la surface limitée et dans les gouttelettes d’eau se comportent conformément aux nos prévisions. Le modèle théorique développé dans cette thèse considère l'accélération des ions en deux étapes. Le champ du laser n'interagit pas directement avec les ions du plasma du à sa masse très élevée. Par contre, les électrons chauds, générés pendant l’interaction de l'impulsion laser avec une cible, produisent les champs électrostatiques importants qui accélèrent les ions aux hautes énergies. Ces champs peuvent être amplifiés si la masse de la cible est suffisamment petite. Nous considérons que la cible a une masse limitée, si toutes ses dimensions sont comparables avec la taille du faisceau laser dans la zone d'interaction. Ces cibles permettent de réduire la dispersion des électrons chauds, et donc d'améliorer la transformation de l'énergie cinétique d'électrons dans l’´energie des ions. Nos simulations numériques indiquent que la taille de cible transverse optimale est égale au diamètre du faisceau laser. Les expériences récentes avec des feuilles minces de la surface limitée ont confirmé que la transformation de l’énergie laser `a l’énergie des ions est plus efficace, l’énergie des ions est plus élevée, et la divergence du faisceau d’ions diminue avec la diminution de la surface de feuille. La physique de l’interaction d'un faisceau laser avec les gouttelettes d’eau est plus complexe, car il faut prendre en compte plusieurs facteurs tels que l'ionisation inhomogène des atomes de la gouttelette et la recombinaison, sa position dans le focus de laser, les collisions des électrons etc. Nous avons modélisé l’interaction de l’impulsion laser avec une gouttelette de diamètre de 100 nm. Dans un petit agrégat des atomes irradié par laser, les électrons sont expulsés par la force pondéromotrice et, pas conséquent, les ions sont accélérés par la force de Coulomb. Nous avons réussi d'expliquer la formation d'un pic dans la fonction de distribution des protons en énergie par l'effet de la répulsion mutuelle entre deux espèces des ions. Finalement, nous avons étudié le transport latéral des électrons dans le cas de l'incidence rasante du faisceau laser sur la cible mince plaine. Avec une série des simulations nous avons démontré qui le transport des électrons accélérés est réalisé par deux mécanismes complémentaires: par le guidage des électrons chauds sur la surface d’avant de la feuille par les champs quasi statiques électrique et magnétique et par la recirculation des électrons entre les faces l'arrière et l'avant de la cibleThe presented thesis is based on a theoretical study of the interaction of femtosecond laser pulses with small-size targets and related phenomena, mainly acceleration of ions. We have employed our relativistic collisionless two-dimensional particle-in-cell code to describe the interaction and subsequent ion acceleration. The theory of ion acceleration and related physics (for example, electron heating mechanisms) have been reviewed as well as computational algorithms used in our simulation code. In the thesis, our obtained results are organized into three main parts: 1) interaction of an intense laser pulse with mass-limited targets; 2) laser proton acceleration in a water spray target; 3) lateral hot electron transport and ion acceleration in thin foils. Our theoretical and numerical studies are accompanied with recent experimental results obtained by cooperating research groups on enhanced ion acceleration in thin foils of reduced surface and on proton acceleration in a cloud of water microdroplets. Since the field of nowadays operating lasers is not sufficient to accelerate directly ions to high energies due to their at least 1000 times larger mass-to-charge ratio compared with electrons, the ion acceleration is mediated by hot electrons creating strong electrostatic fields (a population of electrons heated by the laser wave) in targets of sizes higher or comparable with the laser wavelength or by Coulomb force between ions after electron expulsion in small clusters. Due to reduced target dimensions, the mass-limited targets, defined as the targets having all dimensions comparable with the laser spot size, limit the spread of hot electrons and, thus, the electron kinetic energy is transferred to ions more efficiently. We found via 2D PIC simulations that the optimum transverse target size is about the laser beam diameter. The enhancement of proton energy, laser-to-proton conversion efficiency, and narrower ion angular spread have been observed in recent experiments with thin foil sections and have confirmed our previous theoretical studies. The physics of the laser pulse interaction with water spray is rather complex and includes many phenomena (microdroplet ablation by laser prepulse, inhomogeneous droplet ionization, laser focal spot position in the spray, recombination and collisional effects in the surrounding target material, etc.). We have carried out numerical simulations of the laser pulse interaction with a water microdroplet of diameter of 100 nm, which gives an insight into the physics of ion acceleration in the spray. One can observe a pronounced peak in the proton energy spectra at the cutoff energy, which was explained by mutual interaction between protons and oxygen ions. Finally, we have studied two mechanisms of lateral electron transport in a thin foil - the first is due to hot electron guiding along the foil front surface by generated quasi-static electric and magnetic fields, and the second is caused by the hot electron recirculation (reversing of the normal component of electron velocity when the electron propagating through the foil starts to escape into vacuum, while the transverse velocity is largely unaltered). We found that only a small number of electrons can be guided along the foil surface for large incidence angles (60° and more) of the laser beam on the foil surface, whereas the majority of electrons is laterally transported towards foil edges due to the recirculation through the thin foil. However, electrons guided along the surface can be accelerated to several times higher energy than the recirculating electrons, which enhances the energy of accelerated ions from foil edges
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Masood, Umar. "Radiotherapy Beamline Design for Laser-driven Proton Beams." Helmholtz Zentrum Dresden Rossendorf, 2018. https://tud.qucosa.de/id/qucosa%3A35640.
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Motivation: Radiotherapy is an important modality in cancer treatment commonly using photon beams from compact electron linear accelerators. However, due to the inverse depth dose profile (Bragg peak) with maximum dose deposition at the end of their path, proton beams allow a dose escalation within the target volume and reduction in surrounding normal tissue. Up to 20% of all radiotherapy patients could benefit from proton therapy (PT). Conventional accelerators are utilized to obtain proton beams with therapeutic energies of 70 – 250 MeV. These beams are then transported to the patient via magnetic transferlines and a rotatable beamline, called gantry, which are large and bulky. PT requires huge capex, limiting it to only a few big centres worldwide treating much less than 1% of radiotherapy patients. The new particle acceleration by ultra-intense laser pulses occurs on micrometer scales, potentially enabling more compact PT facilities and increasing their widespread. These laser-accelerated proton (LAP) bunches have been observed recently with energies of up to 90 MeV and scaling models predict LAP with therapeutic energies with the next generation petawatt laser systems. Challenges: Intense pulses with maximum 10 Hz repetition rate, broad energy spectrum, large divergence and short duration characterize LAP beams. In contrast, conventional accelerators generate mono-energetic, narrow, quasi-continuous beams. A new multifunctional gantry is needed for LAP beams with a capture and collimation system to control initial divergence, an energy selection system (ESS) to filter variable energy widths and a large acceptance beam shaping and scanning system. An advanced magnetic technology is also required for a compact and light gantry design. Furthermore, new dose deposition models and treatment planning systems (TPS) are needed for high quality, efficient dose delivery. Materials and Methods: In conventional dose modelling, mono-energetic beams with decreasing energies are superimposed to deliver uniform spread-out Bragg peak (SOBP). The low repetition rate of LAP pulses puts a critical constraint on treatment time and it is highly inefficient to utilize conventional dose models. It is imperative to utilize unique LAP beam properties to reduce total treatment times. A new 1D Broad Energy Assorted depth dose Deposition (BEAD) model was developed. It could deliver similar SOBP by superimposing several LAP pulses with variable broad energy widths. The BEAD model sets the primary criteria for the gantry, i.e. to filter and transport pulses with up to 20 times larger energy widths than conventional beams for efficient dose delivery. Air-core pulsed magnets can reach up to 6 times higher peak magnetic fields than conventional iron-core magnets and the pulsed nature of laser-driven sources allowed their use to reduce the size and weight of the gantry. An isocentric gantry was designed with integrated laser-target assembly, beam capture and collimation, variable ESS and large acceptance achromatic beam transport. An advanced clinical gantry was designed later with a novel active beam shaping and scanning system, called ELPIS. The filtered beam outputs via the advanced gantry simulations were implemented in an advanced 3D TPS, called LAPCERR. A LAP beam gantry and TPS were brought together for the first time, and clinical feasibility was studied for the advanced gantry via tumour conformal dose calculations on real patient data. Furthermore, for realization of pulsed gantry systems, a first pulsed beamline section consisting of prototypes of a capturing solenoid and a sector magnet was designed and tested at tandem accelerator with 10MeV pulsed proton beams. A first air-core pulsed quadrupole was also designed. Results: An advanced gantry with the new ELPIS system was designed and simulated. Simulated results show that achromatic beams with actively selectable beam sizes in the range of 1 – 20 cm diameter with selectable energy widths ranging from 19 – 3% can be delivered via the advanced gantry. ELPIS can also scan these large beams to a 20 × 10 cm2 irradiation field. This gantry is about 2.5 m in height and about 3.5 m in length, which is about 4 times smaller in volume than the conventional PT gantries. The clinical feasibility study on a head and neck tumour patient shows that these filtered beams can deliver state-of-the-art 3D intensity modulated treatment plans.
Experimental characterization of a prototype pulsed beamline section was performed successfully and the synchronization of proton pulse with peak magnetic field in the individual magnets was established. This showed the practical applicability and feasibility of pulsed beamlines. The newly designed pulsed quadrupole with three times higher field gradients than iron-core quadrupoles is already manufactured and will be tested in near future. Conclusion: The main hurdle towards laser-driven PT is a laser accelerator providing beams of therapeutic quality, i.e. energy, intensity, stability, reliability. Nevertheless, the presented advanced clinical gantry design presents a complete beam transport solution for future laser-driven sources and shows the prospect and limitations of a compact laser-driven PT facility. Further development in the LAP-CERR is needed as it has the potential to utilize advanced beam controls from the ELPIS system and optimize doses on the basis of advanced dose schemes, like partial volume irradiation, to bring treatment times further down. To realize the gantry concept, further research, development and testing in higher field and higher (up to 10 Hz) repetition rate pulsed magnets to cater therapeutic proton beams is crucial.
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Snyder, Joseph Clinton. "Leveraging Microscience to Manipulate Laser-Plasma Interactions at Relativistic Intensities." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483626346580096.
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Becker, Georg [Verfasser], Malte Christoph [Gutachter] Kaluza, Paul [Gutachter] Neumayer, and Matthias [Gutachter] Schnürer. "Characterization of laser-driven proton acceleration with contrast-enhanced laser pulses / Georg Becker ; Gutachter: Malte Christoph Kaluza, Paul Neumayer, Matthias Schnürer." Jena : Friedrich-Schiller-Universität Jena, 2021. http://d-nb.info/123917750X/34.
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