Дисертації з теми "Plasma-Based Accelerator"
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Cipiccia, Silvia. "Compact gamma-ray sources based on laser-plasma wakefield accelerator." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23936.
Повний текст джерелаHartwig, Zachary Seth. "An in-situ accelerator-based diagnostic for plasma-material interactions science in magnetic fusion devices." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87488.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references (pages 149-162).
Plasma-material interactions (PMI) in magnetic fusion devices such as fuel retention, material erosion and redeposition, and material mixing present significant scientific and engineering challenges, particularly for the next generation of devices that will move towards reactor-relevant conditions. Achieving an integrated understanding of PMI, however, is severely hindered by a dearth of in-situ diagnosis of the plasma-facing component (PFC) surfaces. To address this critical need, this thesis presents an accelerator-based diagnostic that nondestructively measures the evolution of PFC surfaces in-situ. The diagnostic aims to remotely generate isotopic concentration maps that cover a large fraction of the PFC surfaces on a plasma shot-to-shot timescale. The diagnostic uses a compact, high-current radio-frequency quadrupole accelerator to inject 0.9 MeV deuterons into the Alcator C-Mod tokamak. The tokamak magnetic fields in between plasma shots are used to steer the deuterons to PFCs where the deuterons cause high-Q nuclear reactions with low-Z isotopes ~5 [mu]m into the material. Scintillation detectors measure the induced neutrons and gammas; energy spectra analysis provides quantitative reconstruction of surface concentrations. An overview of the diagnostic technique, known as accelerator-based in-situ materials surveillance (AIMS), and the first AIMS diagnostic on the Alcator C-Mod is given; a description of the complementary simulation tools is also provided. Experimental validation is shown to demonstrate the optimized beam injection into the tokamak, the quantification of PFC surfaces isotopes, and the measurement localization provided by magnetic beam steering. Finally, the first AIMS measurements of fusion fuel retention are presented, demonstrating the local erosion and codeposition of deuterium-saturated boron surface films. The finding confirms that deuterium codeposition with boron is insufficient to account for the net fuel retention in Alcator C-Mod.
by Zachary Seth Hartwig.
Ph. D.
Barnard, Harold Salvadore. "Development of accelerator based spatially resolved ion beam analysis techniques for the study of plasma materials interactions in magnetic fusion devices." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87495.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references (pages 214-218).
Plasma-material interactions (PMI) in magnetic fusion devices pose significant scientific and engineering challenges for the development of steady-state fusion power reactors. Understanding PMI is crucial for the develpment of magnetic fusion devices because fusion plasmas can significantly modify plasma facing components (PFC) which can be severely detrimental to material longevity and plasma impurity control. In addition, the retention of tritium (T) fuel in PFCs or plasma co-deposited material can disrupt the fuel cycle of the reactor while contributing to radiological and regulatory issues. The current state of the art for PMI research involves using accelerator based ion beam analysis (IBA) techniques in order to provide quantitative measurement of the modification to plasma-facing surfaces. Accelerated ~MeV ion beams are used to induce nuclear reactions or scattering, and by spectroscopic analysis of the resulting high energy particles (s', p, n, a, etc.), the material composition can be determined. PFCs can be analyzed to observe erosion and deposition patterns along their surfaces which can be measured with spatial resolution down to the -1 mm scale on depth scales of 10 - 100 pim. These techniques however are inherently ex-situ and can only be performed on PFCs that have been removed from tokamaks, thus limiting analysis to the cumulative PMI effects of months or years of plasma experiments. While ex-situ analysis is a powerful tool for studying the net effects of PMI, ex-situ analysis cannot address the fundamental challenge of correlating the plasma conditions of each experiment to the material surface evolution. This therefore motivates the development of the in-situ diagnostics to study surfaces with comparable diagnostic quality to IBA in order resolve the time evolution of these surface conditions. To address this fundamental diagnostic need, the Accelerator-Based In-Situ Materials Surveillance (AIMS) diagnostic [22] was developed to, for the first time, provide in-situ, spatially resolved IBA measurements inside of the Alcator C-Mod tokamak. The work presented in this thesis provided major technical and scientific contributions to the development and first demonstration AIMS. This included accelerator development, advanced simulation methods, and in-situ measurement of PFC surface properties and their evolution. The AIMS diagnostic was successfully implemented on Alcator C-Mod yielding the first spatially resolved and quantitative in-situ measurements of surface properties in a tokamak, with thin boron films on molybdenum PFCs being the analyzed surface in C-Mod. By combining AIMS neutron and gamma measurements, time resolved and spatially resolved measurements of boron were made, spanning the entire AIMS run campaign which included lower single null plasma discharges, inboard limited plasma discharges, a disruption, and C-Mod wall conditioning procedures. These measurements demonstrated the capability to perform inter shot measurements at a single location, and spatially resolved measurements over longer timescales. This demonstration showed the first in-situ measurements of surfaces in a magnetic fusion device with spatial and temporal resolution which constitutes a major step forward in fusion PMI science. In addition, an external ion beam system was implemented to perform ex-situ ion beam analysis (IBA) for components from Alcator C-Mod Tokamak. This project involved the refurbishment of a 1.7 MV tandem linear accelerator and the creation of a linear accelerator facility to provide IBA capabilities for MIT Plasma Science and Fusion Center. The external beam system was used to perform particle induced gamma emission (PIGE) analysis on tile modules removed after the AIMS measurement campaign in order to validate the AIMS using the well established PIGE technique. From these external PIGE measurements, a spatially resolved map of boron areal density was constructed for a section of C-Mod inner wall tiles that overlapped with the AIMS measurement locations. These measurements showed the complexity of the poloidal and toroidal variation of boron areal density between PFC tiles on the inner wall ranging from 0 to 3pm of boron. Using these well characterized ex-situ measurements to corroborate the in-situ measurements, AIMS showed reasonable agreement with PIGE, thus validating the quantitative surface analysis capability of the AIMS technique.
by Harold Salvadore Barnard.
Sc. D.
McMullin, Nathan K. "Numerical simulation of plasma-based actuator vortex control of a turbulent cylinder wake /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1558.pdf.
Повний текст джерелаGangolf, Thomas. "Intense laser-plasma interactions with gaseous targets for energy transfer and particle acceleration." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX110.
Повний текст джерелаLaser-matter interaction is studied mostly with near-infrared (NIR) lasers as they can generate the most intense pulses. For these lasers, targets between 0.05 to 2.5 times the critical density are challenging to create but offer interesting prospects. In this thesis, novel high-density Hydrogen gas jet targets with densities in this range are used in view of two applications:First, ions are accelerated by collisionless shock acceleration (CSA). Upon interaction of a NIR laser with a slightly overcritical gas jet target, a collimated, quasi-monoenergetic proton beam is generated in forward direction. Simulations indicate the formation of a collisionless shock and acceleration of protons both by the shock and target normal sheath acceleration (TNSA) on the target rear surface under these conditions. These directed, monoenergetic particle bunches are more suitable for many applications than the broadband particle beams already generated routinely.Second, at densities between 0.05 and 0.2 times the critical density, energy is transferred from one laser pulse (pump) to a counterpropagating pulse (seed), via Stimulated Brillouin Backscattering in the strongly-coupled regime (sc-SBS). For the case of broad- band (60 nanometers) pulses, the role of the preionization for pulse propagation and both spontaneous and stimulated Brillouin backscattering are studied, including the influence of the chirp. It is shown that for narrower bandwidths, the seed pulse is ampli- fied by tens of millijoules, and signatures of efficient amplification and pump depletion are found. This concept aims at amplifying laser pulses to powers above the damage thresholds of solid state amplifiers
PEREGO, CLAUDIO. "Target normal sheath acceleration for laser-driven ion generation: advances in theoretical modeling." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2013. http://hdl.handle.net/10281/41758.
Повний текст джерелаHillenbrand, Steffen [Verfasser], and A. S. [Akademischer Betreuer] Müller. "Study of Plasma-Based Acceleration for High Energy Physics and Other Applications / Steffen Hillenbrand. Betreuer: A.-S. Müller." Karlsruhe : KIT-Bibliothek, 2013. http://d-nb.info/1054397163/34.
Повний текст джерелаMehrling, Timon Johannes [Verfasser], and Jens [Akademischer Betreuer] Osterhoff. "Theoretical and numerical studies on the transport of transverse beam quality in plasma-based accelerators / Timon Johannes Mehrling. Betreuer: Jens Osterhoff." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://d-nb.info/1064077358/34.
Повний текст джерелаBeaurepaire, Benoit. "Développement d’un accélérateur laser-plasma à haut taux de répétition pour des applications à la diffraction ultra-rapide d’électrons." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX013/document.
Повний текст джерелаElectronic microscopy and electron diffraction allowed the understanding of the organization of atoms in matter. Using a temporally short source, one can measure atomic displacements or modifications of the electronic distribution in matter. To date, the best temporal resolution for time resolved diffraction experiments is of the order of a hundred femtoseconds (fs). Laser-plasma accelerators are good candidates to reach the femtosecond temporal resolution in electron diffraction experiments. Moreover, these accelerators can operate at a high repetition rate, allowing the accumulation of a large amount of data.In this thesis, a laser-plasma accelerator operating at the kHz repetition rate was developed and built. This source generate electron bunches at 100 keV from 3 mJ and 25 fs laser pulses. The physics of the acceleration has been studied, and the effect of the laser wavefront on the electron transverse distribution has been demonstrated.The first electron diffraction experiments with such a source have been realized. An experiment, which was a proof of concept, showed that the quality of the source permits to record nice diffraction patterns on gold and silicium foils. In a second experiment, the structural dynamics of a silicium sample has been studied with a temporal resolution of the order of a few picoseconds.The electron bunches must be accelerated to relativistic energies, at a few MeV, to reach a sub-10 fs temporal resolution. A numerical study showed that ultra-short electron bunches can be accelerated using 5 fs and 5 mJ laser pulses. A temporal resolution of the order of the femtosecond could be reached using such bunches for electron diffraction experiments. Finally, an experiment of the ionization-induced compression of the laser pulses has been realized. The pulse duration was shorten by a factor of 2, and the homogeneity of the process has been studied experimentally and numerically
Yi, Sunghwan. "Injection in plasma-based electron accelerators." 2012. http://hdl.handle.net/2152/19461.
Повний текст джерелаtext
FILIPPI, FRANCESCO. "Plasma source characterization for plasma-based acceleration experiments." Doctoral thesis, 2017. http://hdl.handle.net/11573/1102637.
Повний текст джерелаNicoul, Matthieu [Verfasser]. "Time-resolved X-ray diffraction with accelerator- and laser-plasma-based X-ray sources / von Matthieu Nicoul." 2010. http://d-nb.info/1008993468/34.
Повний текст джерелаHo, Yen-cheng, and 何彥政. "Induction of electron injection and X-ray generation in a plasma -waveguide -based laser wakefield electron accelerator." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/50624642215293304008.
Повний текст джерела國立中央大學
物理學系
101
Laser driven wakefield is capable of sustaining field in excess of 1 GV/cm, making it a promising candidate for the next-generation electron accelerator. The development of chirp pulse amplification boosts the power of laser pulse to terawatt (TW) or even petawatt (PW) level, making it possible to drive a large-amplitude plasma wave to accelerate electrons by the poderomotive force of the intense focused laser pulse. This technique has achieved GeV electron energy in centimeter scale and is being investigated as a driver for generating bright photons with spectrum ranging from THz to X-rays. The most important issues in this field are injection and acceleration process in the driven plasma wave, which determines the quality and shot-to-shot stability of the electron beam and the highest energy gain one can obtain from the accelerator. This thesis reports the efforts and accomplishments on the development of a plasma-waveguide-based Laser wakefield accelerator with two kinds of new electron injection scheme and channel betatron radiated X-ray source. In the first part of my work, a systematic experimental study on injection of electrons in a gas-jet-based laser wakefield accelerator via ionization of dopant was conducted. The pump-pulse threshold energy for producing a quasimonoenergetic electron beam was significantly reduced by doping the hydrogen gas jet with argon atoms, resulting in a much better spatial contrast of the electron beam. Furthermore, laser wakefield electron acceleration in an optically preformed plasma waveguide based on the axicon-ignitor-heater scheme was achieved. It was found that doping with argon atoms can also lower the pump-pulse threshold energy in the case with a plasma waveguide. In the second part of my work, a variable three-dimensionally structured plasma waveguide was fabricated by adding a transverse heater pulse into the axicon-ignitor-heater-scheme. With this technique, induction of electron injection in a plasma-waveguide-based laser wakefield accelerator was achieved and resulted in production of a monoenergetic electron beam. The injection is correlated with a section of expanding cross-section in the plasma waveguide. Moreover, the intensity of the X-ray beam produced by the electron bunch in betatron oscillation was greatly enhanced with a transversely shifted section in the plasma waveguide. The technique opens the route to a compact hard x-ray pulse source.
Chang, Ying-Li, and 張穎力. "Controlled Electron Injection In a Plasma-waveguide-based Laser Wakefield Accelerator By Implementation Of a Density Down Ramp." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/40266242472822517972.
Повний текст джерела國立中正大學
物理學系暨研究所
100
Laser wakefield electron accelerator has been demonstrated to have the capability of generating GeV-energy, low-emittance, high-stability electron pulses in centimeter scale length. It has shown great potential to become the key technology for next-generation TeV collider and various table-top ultrashort-pulse photon sources of wavelength ranging from THz to gamma-ray. These applications require an electron beam with high quality and stability, both of which are determined by finely controlled injection and acceleration processes in a laser-driven plasma wave. Here we report demonstration of production of a low-energy-spread electron beam via injection by longitudinal wave-breaking induced in a density down ramp in a plasma waveguide. In this scheme, the plasma waveguide is generated by using the axicon-ignitor-heater scheme, and an additional transverse heater pulse passing through a knife edge is used to produce longitudinal density variation in the plasma waveguide. This technique allows us to freely control the position and slope of the density ramp and to observe them with probing interferometry. It was observed that generation of a high-energy quasi-monoenergetic electron beam occurs only when the transverse heater pulse produces a density down ramp, and the probability of production varies with the position of density ramp. Good guiding of the pump laser pump was still maintained under the condition of presence of density ramps and high pump-pulse energy. The energy spread of the produced electron beam can be as low as 1%. The tunability of the density ramp allows us to clarify the ramp injection process and to optimize the quality of the electron beam. With this technique of fabrication of three-dimensional plasma density structure, integration of electron injector, accelerator, and x-ray free-electron laser in a single plasma waveguide may be achieved.
Jhou, Jun-Guan, and 周君冠. "Enhancement of X-ray pulse production from betatron oscillation of the electron bunch in a plasma-waveguide-based laser wakefield accelerator by modification of the waveguide structure." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/55104410896317492265.
Повний текст джерела國立臺灣大學
物理研究所
101
Here we demonstrate the use of laser-driven plasma accelerators, which accelerate high-charge electron beams to high energy in short distances. The particles being accelerated in the plasma accelerator also undergo transverse (betatron) oscillations to intrinsically ultrafast beams of hard X-rays. The experiment was performed at National Central University, Taiwan, using a 100-TW-class Ti:sapphire laser system with 10-Hz pulse repetition rate. Five laser beams from this system were used for the experiment. The axicon ignitor and heater pulses were used to fabricate a ∼ 1-cm length in full width at half maximum (FWHM) uniform plasma waveguide in a gas jet. The 1.1-J, 40-fs pump pulse was coupled into the plasma waveguide at a delay of 1.9 ns with respect to the axicon heater pulse to excite a plasma wave (plasma bubble) which can accelerate electrons. The focal spot size was 10 μm in FWHM. By adding a transverse heater 1 pulse into the axicon ignitor-heater scheme for producing a plasma waveguide, a variable three-dimensionally structured plasma waveguide can be fabricated. With this technique, electron injection in a plasma-waveguide-based laser wakefield accelerator was achieved and resulted in production of electron beam energy large than 200 MeV. Then a 116-mJ, 210-ps transverse heater 2 pulse was used to introduce lower density spatial gaps between uniform plasma density sections that behind the fabricated plasma waveguide. When accelerated electrons that enter the depression at the proper phase in their betatron oscillation will increase their transverse displacement, thus exiting the depression with larger betatron amplitude. This technique opens a route to a compact hard-X-ray pulse source. We could produce x-ray with photon energies in the range of 1–10 keV by using lower density spatial gaps between uniform plasma density sections. If we compare laser- driven betatron-radiation x-ray source with conventional particle accelerator facilities, we find the size is significantly smaller and the cost is much cheaper. This reduces the size of the synchrotron source from the tens of meters to the centimeter scale, simultaneously accelerating and wiggling the electron beam. Then the betatron radiation has intrinsically striking features for ultra-fast imaging. Therefore laser- driven betatron-radiation x-ray source has the potential to be a table top hard-X-ray pulse source.
Dong, Peng. "Laboratory visualization of laser-driven plasma accelerators in the bubble regime." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-08-1881.
Повний текст джерелаtext
Sahai, Aakash Ajit. "On Certain Non-linear and Relativistic Effects in Plasma-based Particle Acceleration." Diss., 2015. http://hdl.handle.net/10161/10534.
Повний текст джерелаPlasma-based particle acceleration holds the promise to make the applications that revolve around accelerators more affordable. The central unifying theme of this dissertation is the modeling of certain non-linear and relativistic phenomena in plasma dynamics to devise mechanisms that benefit plasma-accelerators. Plasma acceleration presented here has two distinct flavors depending upon the accelerated particle mass which dictates the acceleration structure velocity and potential. The first deals with ion acceleration, where acceleration structure velocities are a significant fraction of the speed of light, with major applications in medicine. The second focusses on the acceleration of electrons and positrons for light-sources and colliders where the acceleration structures are wakefields with phase-velocities near the speed of light.
The increasing Lorentz factor of the laser-driven electron quiver momentum forms the basis of Relativistically Induced Transparency Acceleration (RITA) scheme of ion acceleration. Lighter ions are accelerated by reflecting off a propagating acceleration structure, referred to as a snowplow, formed by the compression of ponderomotively driven critical layer electrons excited in front of a high intensity laser pulse in a fixed-ion plasma. Its velocity is controlled by tailoring the laser pulse rise-time and rising density gradient scale-length. We analytically model its induced transparency driven propagation with a 1-D model based on the linearized dispersion relation. The model is shown to be in good agreement with the weakly non-linear simulations. As the density compression rises into the strongly non-linear regime, the scaling law predictions remain accurate but the model does not exactly predict the RITA velocity or the accelerated ion-energy. Multi-dimensional plasma effects modify the laser radial envelope by self-focussing in the rising density gradient which can be integrated into our model and filamentation which is mitigated by a matched laser focal spot-size. We show that the critical layer motion in RITA compares favorably to the bulk-plasma motion driven by radiation pressure or collision-less shocks.
Non-linear mixing of the laser, incident on and reflected off the propagating critical layer modulates its envelope affecting the acceleration structure velocity and potential, in the process setting up a feedback loop. For long pulses the envelope distortion grows with time, disrupting the accelerated ion-beam spectral shape. We model the Chirp Induced Transparency Acceleration (ChITA) mechanism that over- comes this effect by introducing decoherence through a frequency chirp in the laser.
In a rising density gradient, the non-linearity of electron trajectories leads to the phase-mixing self-injection of electrons into high phase-velocity plasma wakefields. The onset of trapping depends upon the wake amplitude and the density gradient scale-length. This self-injection mechanism is also applicable to controlling the spuriously accelerated electrons that affect the beam-quality.
Non-linear ion dynamics behind a train of asymmetric electron-wake excites a cylindrical ion-soliton similar to the solution of the cylindrical Korteweg-de Vries (cKdV) equation. This non-linear ion-wake establishes an upper limit on the repetition rate of the future plasma colliders. The soliton is excited at the non-linear electron wake radius due to the time-asymmetry of its radial fields. In a non-equilibrium wake heated plasma the radial electron temperature gradient drives the soliton. Its radially outwards propagation leaves behind a partially-filled ion-wake channel.
We show positron-beam driven wakefield acceleration in the ion-wake channel. Optimal positron-wakefield acceleration with linear focussing fields is shown to require a matched hollow-plasma channel of a radius that depends upon the beam properties.
Dissertation