Dissertations / Theses on the topic 'Laser driven proton acceleration'
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1
Sinigardi, Stefano <1985>. "Laser driven proton acceleration and beam shaping." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6230/.
Abstract:
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.
2
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.
3
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.
Abstract:
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.
4
Masood, Umar. "Radiotherapy Beamline Design for Laser-driven Proton Beams." Helmholtz Zentrum Dresden Rossendorf, 2018. https://tud.qucosa.de/id/qucosa%3A35640.
Abstract:
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.
5
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.
6
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.
7
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.
8
Gao, Ying [Verfasser], and Jörg [Akademischer Betreuer] Schreiber. "High repetition rate laser driven proton source and a new method of enhancing acceleration / Ying Gao ; Betreuer: Jörg Schreiber." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1214180353/34.
9
Zeil, Karl [Verfasser], Roland [Akademischer Betreuer] Sauerbrey, and Jörg [Akademischer Betreuer] Schreiber. "Efficient laser-driven proton acceleration in the ultra-short pulse regime / Karl Zeil. Gutachter: Roland Sauerbrey ; Jörg Schreiber. Betreuer: Roland Sauerbrey." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://d-nb.info/1068153164/34.
10
Wong, Liang Jie. "Laser-driven electron acceleration in infinite vacuum." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66479.
Abstract:
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.
11
Romagnani, L. "Laser-plasma investigations employing laser-driven proton probes." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426587.
12
Schreiber, Jörg. "Ion Acceleration driven by High-Intensity Laser Pulses." Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-58421.
13
Schreiber, Jörg. "Ion acceleration driven by high-intensity laser pulses." [S.l.] : [s.n.], 2006. http://edoc.ub.uni-muenchen.de/archive/00005842.
14
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.
15
Morita, Toshimasa. "Studies on the Proton Acceleration by a Laser Pulse." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120913.
16
Henig, Andreas. "Advanced Approaches to High Intensity Laser-Driven Ion Acceleration." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-114831.
17
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.
18
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.
Abstract:
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.
19
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.
20
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.
Abstract:
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.
21
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.
22
Doche, Antoine. "Particle acceleration with beam driven wakefield." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX023/document.
Abstract:
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
23
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.
Abstract:
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.
24
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.
Abstract:
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.
25
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.
Abstract:
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.
26
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.
Abstract:
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.
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Flacco, A. "Experimental Study of Proton Acceleration with Ultra-High Intensity, High Contrast Laser Beam." Phd thesis, Ecole Polytechnique X, 2008. http://pastel.archives-ouvertes.fr/pastel-00005616.
Abstract:
La production de faisceaux énergétiques d'ions/protons avec des impulsions laser à intensités relativistes (I>10^{18}W/cm^2) a reçu, au cours des dernières années, un intérêt croissant parmi les scientifiques travaillant dans les domaines de l'optique, de la physique des plasmas et des accélérateurs. Une fraction des électrons est chauffée à haute température lors de l'interaction entre une impulsion laser femtoseconde et un plasma surdense. Les ions et les protons sont extraits et accélérés par la séparation de charge qui est produite pendant l'expansion du plasma. Les résultats présentés dans ce manuscrit décrivent la réalisation d'expériences d'accélération d'ions avec un système laser à haute puissance et à haut contraste (XPW). Deux expériences préparatoires sont réalisées, afin d'étudier l'interaction entre le piédestal d'une impulsion laser et une cible. L'expansion d'un plasma créé par laser à intensité moyenne est mesurée par interférométrie; l'évolution de la longueur de son gradient de densité est déduite par les cartes de densité électronique, mesurées à différents instants. La variation de la réflectivité absolue d'une cible mince d'aluminium est mise en corrélation avec la température électronique afin de contrôler le débouché du choc produit par le laser. La corrélation entre les deux expériences est finalement utilisée pour définir le conditions optimales pour l'accélération des protons. Des expériences d'accélération de protons avec un laser à haut contraste, la construction et la validation d'un spectromètre (Galette a Micro-canaux et Parabole Thomson), ainsi que des autres détails sur le montage sont présentés. Les résultats ainsi obtenus montrent que l'amélioration du contraste permet d'utiliser des cibles plus minces et de produire des conditions d'interaction plus stables et contrôlables. Des faisceaux des protons ayant énergie cinétique supérieure à 4MeV sont produits, avec une stabilité tir à tir meilleure de 4% rms. L'accélération des protons avec deux impulsions laser confirme que l'absorption d'énergie laser est augmentée dans le cas des cibles pre-chauffées par une impulsion laser avec les bons paramètres.
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Flacco, Alessandro. "Experimental study of proton acceleration with ultra-high intensity, high contrast laser beam." École polytechnique, 2010. http://www.theses.fr/2008EPXX0071.
Abstract:
La production de faisceaux énergétiques d'ions/protons avec des impulsions laser à intensités relativistes (I>10^{18}W/cm^2) a reçu, au cours des dernières années, un intérêt croissant parmi les scientifiques travaillant dans les domaines de l'optique, de la physique des plasmas et des accélérateurs. Une fraction des électrons est chauffée à haute température lors de l'interaction entre une impulsion laser femtoseconde et un plasma surdense. Les ions et les protons sont extraits et accélérés par la séparation de charge qui est produite pendant l'expansion du plasma. Les résultats présentés dans ce manuscrit décrivent la réalisation d'expériences d'accélération d'ions avec un système laser à haute puissance et à haut contraste (XPW). Deux expériences préparatoires sont réalisées, afin d'étudier l'interaction entre le piédestal d'une impulsion laser et une cible. L'expansion d'un plasma créé par laser à intensité moyenne est mesurée par interférométrie; l'évolution de la longueur de son gradient de densité est déduite par les cartes de densité électronique, mesurées à différents instants. La variation de la réflectivité absolue d'une cible mince d'aluminium est mise en corrélation avec la température électronique afin de contrôler le débouché du choc produit par le laser. La corrélation entre les deux expériences est finalement utilisée pour définir le conditions optimales pour l'accélération des protons. Des expériences d'accélération de protons avec un laser à haut contraste, la construction et la validation d'un spectromètre (Galette a Micro-canaux et Parabole Thomson), ainsi que des autres détails sur le montage sont présentés. Les résultats ainsi obtenus montrent que l'amélioration du contraste permet d'utiliser des cibles plus minces et de produire des conditions d'interaction plus stables et contrôlables. Des faisceaux des protons ayant énergie cinétique supérieure à 4MeV sont produits, avec une stabilité tir à tir meilleure de 4% rms. L'accélération des protons avec deux impulsions laser confirme que l'absorption d'énergie laser est augmentée dans le cas des cibles pre-chauffées par une impulsion laser avec les bons paramètresThe production of energetic proton/ion beams with laser pulses at relativistic intensities (I>10^{18}W/cm^2) has received, in the past few years, increasing interest from the scientific community in plasma, optics and accelerator physics. A fraction of electrons is heated to high temperature during the ultrafast interaction between a femtosecond laser pulse and an overdense plasma. Ions and protons are extracted and accelerated by the charge separation set up during the expansion of the plasma. The results presented in this manuscript report on the realization of ion acceleration experiments using a high contrast (XPW) multi-terawatt laser system. Two preparatory experiments are set up, aiming to study the pedestal of a laser pulse interacting with the target. The expansion of a plasma created by a laser at moderate intensity is measured by interferometry; the evolution of the density gradient length is deduced from the electron density maps at different moments. The variation of the absolute reflectivity of a thin aluminium foil is correlated to the electron temperature and is used to monitor the arrival time of the laser produced shock. The crossing between the two experiments is finally used to define the optimum condition for proton acceleration. Proton acceleration experiments with high contrast laser are reported, including the construction and the validation of a real-time, single shot ion spectrometer (Micro-channel Plate and Thomson Parabola), and other details of the realised setup. The obtained results show that the increased contrast enables the use of thinner targets and the production of more stable and controllable interaction conditions. Proton beams with kinetic energy higher than 4 MeV are produced, with a shot-to-shot stability better than 4% rms. Proton acceleration experiment with two laser beams confirms that the laser energy absorption is enhanced when the target is pre-heated by a laser pulse with proper parameters
29
Brenner, Ceri M. "Laser-driven proton beams : mechanisms for spectral control and efficiency enhancement." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18234.
Abstract:
This thesis reports on investigations of proton acceleration driven by the interaction of short, intense laser pulses with thin, solid targets. Laser-driven plasma interactions are used to establish accelerating quasi-electrostatic field gradients, on the rear surface of the target, that are orders of magnitude higher than the current limit of conventional, radio-frequency-based accelerator technology. The resulting high energy (multi-MeV) proton beams are highly laminar, have ultra-low emittance, and the inherently broad energy spectrum is particularly effective for use in proton imaging, heating and transmutation applications. This thesis reports on a series of investigations carried out to explore routes towards control of the spectral properties of laser-driven proton sources and optimisation of laser-to-proton energy conversion efficiency. The dependence of laser accelerated proton beam properties on laser energy and focal spot size in the interaction of an intense laser pulse with an ultra-thin foil is explored at laser intensities of 1016-1018 W/cm2. The results indicate that whilst the maximum proton energy is dependent on both these laser pulse parameters, the total number of protons accelerated is primarily related to the laser pulse energy. A modification to current analytical models of the proton acceleration, to take account of lateral transport of electrons on the target rear surface, is suggested to account for the experimental findings. The thesis also reports on an investigation of optical control of laser-driven proton acceleration, in which two relativistically intense laser pulses, narrowly separated in time, are used. This novel approach is shown to deliver a significant enhancement in the coupling of laser energy to medium energy (5-30 MeV) protons, compared to single pulse irradiation. The 'double-pulse' mechanism of proton acceleration is investigated in combination with thin targets, for which refluxing of hot electrons between the target surfaces can lead to optimal conditions for coupling laser drive energy into the proton beam. A high laser-to-proton conversion efficiency is measured when the delay between the pulses is optimised at 1 ps. The subsequent effect of double-pulse drive on the angular distribution of the proton beam is also explored for thick targets.
30
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.
31
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.
Abstract:
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.
32
Robinson, Alexander Patrick Lowell. "Kinetic simulation of fast electron transport and proton acceleration in ultraintense laser-solid interactions." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424440.
33
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.
34
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.
35
Ahmed, Hamad. "Optimisation of laser driven proton beams and their applications to plasma radiography." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602406.
Abstract:
The interaction of ultra-intense laser pulses >1018W/cm2 with thin foils drives the acceleration of protons to multi-MeV energies. Proton beam has unique properties such as low emittance, short pulse duration and high particle flux. However, the beams usually • exhibit large envelope divergence and quasi-Maxwellian energy spectra, which might be undesirable for a range of foreseen applications. Hot electrons generated during the interaction of intense lasers with foil targets escape the foil, charging it to potential of the order of the hot electron temperature. It is observed that the charge flows towards the ground with a velocity close to the speed of light in a localised pulse of a Gaussian profile with 6ps rise and 15ps decay, which retains its temporal profile over a few centimetres. Based on these findings, novel target geometry is envisioned to create an electrostatic lens which simultaneously focuses/collimates the proton beam and allows energy selection. This electrostatic lens demonstrates a reduction in beam diameter by 75% and an enhancement of the proton flux by an order of magnitude for 6.5 MeV protons in comparison to typical divergent proton beam. Particle tracing simulations corroborate the dynamics nature of the lens. Laser driven proton beam is employed as proton radiography technique to investigate the expansion of ablated plasma created by the interaction of intense laser >1015W/cm2 with solid target, into low density background plasma. High temporal and spatial resolution of the technique allows detection of the precursory stages that lead to formation of an electrostatic collision less shock at the boundary of blast shell of the expanding laser ablated plasma. The evolution of the electrostatic potential associated with the shock unveils the transition from a double layer into a symmetric shock structure, stabilized by ion reflection at the shock front. A PlC simulation supports the existence of super-critical electrostatic shocks.
36
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.
Abstract:
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
37
Almomani, Ali [Verfasser], Ulrich [Akademischer Betreuer] Ratzinger, and Ingo [Akademischer Betreuer] Hofmann. "RF acceleration of intense laser generated proton bunches / Ali Almomani. Gutachter: Ulrich Ratzinger ; Ingo Hofmann." Frankfurt am Main : Univ.-Bibliothek Frankfurt am Main, 2012. http://d-nb.info/1044093757/34.
38
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.
Abstract:
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
39
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.
Abstract:
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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Würl, Matthias [Verfasser], and Katia [Akademischer Betreuer] Parodi. "On the spectrometry of laser-accelerated particle bunches and laser-driven proton radiography / Matthias Würl ; Betreuer: Katia Parodi." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1196008949/34.
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Snavely, Richard Adolph. "Physics of laser driven relativistic plasmas, energetic X-rays, proton beams and relativistic electron transport in Petawatt laser experiments /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Knetsch, Alexander [Verfasser], and Bernhard [Akademischer Betreuer] Hidding. "Acceleration of laser-injected electron beams inan electron-beam driven plasma wakefieldaccelerator / Alexander Knetsch ; Betreuer: Bernhard Hidding." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://d-nb.info/115388433X/34.
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Bajlekov, Svetoslav. "Towards a free-electron laser driven by electrons from a laser-wakefield accelerator : simulations and bunch diagnostics." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:99f9f13a-d0c2-4dd8-a9a4-13926621c352.
Abstract:
This thesis presents results from two strands of work towards realizing a free-electron laser (FEL) driven by electron bunches generated by a laser-wakefield accelerator (LWFA). The first strand focuses on selecting operating parameters for such a light source, on the basis of currently achievable bunch parameters as well as near-term projections. The viability of LWFA-driven incoherent undulator sources producing nanojoule-level pulses of femtosecond duration at wavelengths of 5 nm and 0.5 nm is demonstrated. A study on the prospective operation of an FEL at 32 nm is carried out, on the basis of scaling laws and full 3-D time-dependent simulations. A working point is selected, based on realistic bunch parameters. At that working point saturation is expected to occur within a length of 1.6 m with peak power at the 0.1 GW-level. This level, as well as the stability of the amplification process, can be improved significantly by seeding the FEL with an external radiation source. In the context of FEL seeding, we study the ability of conventional simulation codes to correctly handle seeds from high-harmonic generation (HHG) sources, which have a broad bandwidth and temporal structure on the attosecond scale. Namely, they violate the slowly-varying envelope approximation (SVEA) that underpins the governing equations in conventional codes. For this purpose we develop a 1-D simulation code that works outside the SVEA. We carry out a set of benchmarks that lead us to conclude that conventional codes are adequately capable of simulating seeding with broadband radiation, which is in line with an analytical treatment of the interaction. The second strand of work is experimental, and focuses on on the use of coherent transition radiation (CTR) as an electron bunch diagnostic. The thesis presents results from two experimental campaigns at the MPI für Quantenoptik in Garching, Germany. We present the first set of single-shot measurements of CTR over a continuous wavelength range from 420 nm to 7 μm. Data over such a broad spectral range allows for the first reconstruction of the longitudinal profiles of electron bunches from a laser-wakefield accelerator, indicating full-width at half-maximum bunch lengths around 1.4 μm (4.7 fs), corresponding to peak currents of several kiloampères. The bunch profiles are reconstructed through the application of phase reconstruction algorithms that were initially developed for studying x-ray diffraction data, and are adapted here for the first time to the analysis of CTR data. The measurements allow for an analysis of acceleration dynamics, and suggest that upon depletion of the driving laser the accelerated bunch can itself drive a wake in which electrons are injected. High levels of coherence at optical wavelengths indicate the presence of an interaction between the bunch and the driving laser pulse.
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Schwartz, Brook-Eden 1979. "Imaging the burn region of laser driven implosions on OMEGA using the proton core imaging spectroscope." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29443.
Abstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2004.Includes bibliographical references (p. 143).
The first measurements of the nuclear burn region of OMEGA implosions have been made with the Proton Core Imaging Spectroscope (PCIS). Using CR-39 nuclear track detectors, PCIS applies the technique of penumbral imaging to measure the radial profile of D-D and D-3He protons produced by implosions of D2-3He-filled capsules. For capsules with 20 [mu]m-CH shells, images of D-3He protons resulted in Gaussian profiles with an average l/e radius of [approx.]35 [mu]m. Gaussian profiles inferred from the D-3He protons and D-D protons produced by implosions of 2 [mu]tm SiO2-shell capsules had average l/e radii of 60 [mu]m and 94 [mu]m, respectively. [mu]m and 94 [mu]m, respectively.
by Brook-Eden Schwartz.
S.M.
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Masood, Umar [Verfasser], Wolfgang [Akademischer Betreuer] Enghard, and Peter [Gutachter] Michel. "Radiotherapy Beamline Design for Laser-driven Proton Beams / Umar Masood ; Gutachter: Peter Michel ; Akademischer Betreuer: Wolfgang Enghard." Dresden : Technische Universität Dresden, 2019. http://d-nb.info/1234398478/34.
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Pommarel, Loann. "Transport and control of a laser-accelerated proton beam for application to radiobiology." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX001/document.
Abstract:
L’accélération de particules par interaction laser-plasma est une alternative prometteuse aux accélérateurs conventionnels qui permettrait de rendre plus compactes les machines du futur dédiées à la protonthérapie. Des champs électriques extrêmes de l’ordre du TV/m sont créés en focalisant une impulsion laser ultra-intense sur une cible solide mince de quelques micromètres d’épaisseur, ce qui produit un faisceau de particules de haute énergie. Ce dernier contient des protons ayant une énergie allant jusqu’à la dizaine de mégaélectron-volts, et est caractérisé par une forte divergence angulaire et un spectre en énergie très étendu.Le but de cette thèse est de caractériser parfaitement un accélérateur laser-plasma afin de produire un faisceau de protons stable, satisfaisant les critères d'énergie, de charge et d'homogénéité de surface requis pour son utilisation en radiobiologie. La conception, la réalisation et l’implémentation d’un système magnétique, constitué d'aimants permanents quadripolaires ont été optimisés au préalable avec des simulations numériques. Ce système permet d’obtenir un faisceau de protons ayant un spectre en énergie qui à été mise en forme, et dont le profil est uniforme sur une surface de taille adaptée aux échantillons biologiques.Une dosimétrie absolue et en ligne a également été établie, permettant le contrôle de la dose délivrée en sortie. Pour cela, une chambre d'ionisation à transmission, précédemment calibrée sur un accélérateur à usage médical de type cyclotron, a été mise en place sur le trajet du faisceau de protons. Des simulations Monte Carlo ont ensuite permis de calculer la dose déposée dans les échantillons. Ce système compact autorise maintenant de définir un protocole expérimental rigoureux pour la poursuite d’expériences in vitro de radiobiologie. De premières irradiations de cellules cancéreuses ont été ainsi réalisées in vitro, ouvrant la voie à l’exploration des effets de rayonnements ionisants pulsés à haut débit de dose sur les cellules vivantesParticle acceleration by laser-plasma interaction is a promising alternative to conventional accelerators that could make future devices dedicated to protontherapy more compact. Extreme electric fields in the order of TV/m are created when an ultra-intense laser pulse is focused on a thin solid target with a thickness of a few micrometers, which generates a beam of highly energetic particles. The latter includes protons with energies up to about ten megaelectron-volts and characterised by a wide angular divergence and a broad energy spectrum.The goal of this thesis is to fully characterise a laser-based accelerator in order to produce a stable proton beam meeting the energy, charge and surface homogeneity requirements for radiobiological experiments. The design, realisation and implementation of a magnetic system made of permanent magnet quadrupoles were optimised beforehand through numerical simulations. It enables to obtain a beam with a shaped energy spectrum and with a uniform profile over a surface with a size adapted to the biological samples.Deferred and online dosimetry was setup to monitor the delivered output dose. For that purpose, a transmission ionisation chamber, previously calibrated absolutely on a medical proton accelerator, was used. Monte Carlo simulations enabled to compute the dose deposited into the samples. This compact system allows now to define a rigorous experimental protocol for in vitro radiobiological experiments. First experiments of cancer cell irradiation have been carried out, paving the way for the exploration of the effects of pulsed ionizing radiations at extremely high dose rates on living cells
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Naundorf, Holger. "Ultrafast laser driven proton dynamics in gas- and condensed phase Ultraschnelle lasergetriebene Protonendynamik in Gas- und kondensierter Phase /." [S.l. : s.n.], 2002. http://www.diss.fu-berlin.de/2003/65/index.html.
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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.
Abstract:
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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Busold, Simon [Verfasser], Markus [Akademischer Betreuer] Roth, and Oliver [Akademischer Betreuer] Boine-Frankenheim. "Construction and characterization of a laser-driven proton beamline at GSI / Simon Busold. Betreuer: Markus Roth ; Oliver Boine-Frankenheim." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2014. http://d-nb.info/1110792204/34.
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Gonoskov, Arkady. "Ultra-intense laser-plasma interaction for applied and fundamental physics." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-84245.
Abstract:
Rapid progress in ultra-intense laser technology has resulted in intensity levels surpassing 1022 W/cm2, reaching the highest possible density of electromagnetic energy amongst all controlled sources available in the laboratory. During recent decades, fast growth in available intensity has stimulated numerous studies based on the use of high intensity lasers as a unique tool for the initiation of nonlinear behavior in various basic systems: first molecules and atoms, then plasma resulting from the ionization of gases and solids, and, finally, pure vacuum. Apart from their fundamental importance, these studies reveal various mechanisms for the conversion of a laser pulse's energy into other forms, opening up new possibilities for generating beams of energetic particles and radiation with tailored properties. In particular, the cheapness and compactness of laser based sources of energetic protons are expected to make a revolution in medicine and industry. In this thesis we study nonlinear phenomena in the process of laser radiation interacting with plasmas of ionized targets. We develop advanced numerical tools and use them for the simulation of laser-plasma interactions in various configurations relating to both current and proposed experiments. Phenomenological analysis of numerical results helps us to reveal several new effects, understand the physics behind them and develop related theoretical models capable of making general conclusions and predictions. We develop target designs to use studied effects for charged particle acceleration and for the generation of attosecond pulses of unprecedented intensity. Finally, we analyze prospects for experimental activity at the upcoming international high intensity laser facilities and uncover a basic effect of anomalous radiative trapping, which opens up new possibilities for fundamental science.