Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 39
Book Description
Simulations on Laser Wakefield Acceleration in Plasma Guiding Channel
Author: Plasma Channel Guided Laser Wakefield Accelerator
Author: Cameron Guy Robinson GeddesPublisher:
ISBN:
Category :
Languages : en
Pages : 436
Book Description
Simulation of Electron Post-acceleration in a Two-stage Laser Wakefield Accelerator
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 5
Book Description
Electron bunches produced in self-modulated laser wakefield experiments usually have a broad energy spectrum, with most electrons at low energy (1-3 MeV) and only a small fraction at high energy. We propose and investigate further acceleration of such bunches in a channel-guided resonant laser wakefield accelerator. Two-dimensional simulations with and without the effects of self-consistent beam loading are performed and compared. These results indicate that it is possible to trap about 40 percent of the injected bunch charge and accelerate this fraction to an average energy of about 50 MeV in a plasma channel of a few mn.
Laser Wakefield Acceleration in Tapered Plasma Channels
Author: Wolf RittershoferProgress on Laser Plasma Accelerator Development Using Transverselyand Longitudinally Shaped Plasmas
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 10
Book Description
A summary of progress at Lawrence Berkeley National Laboratory is given on: (1) experiments on down-ramp injection; (2) experiments on acceleration in capillary discharge plasma channels; and (3) simulations of a staged laser wakefield accelerator (LWFA). Control of trapping in a LWFA using plasma density down-ramps produced electron bunches with absolute longitudinal and transverse momentum spreads more than ten times lower than in previous experiments (0.17 and 0.02 MeV Ic FWHM, respectively) and with central momenta of 0.76 +- 0.02 MeV Ic, stable over a week of operation. Experiments were also carried out using a 40 TW laser interacting with a hydrogen-filled capillary discharge waveguide. For a 15 mm long, 200 mu m diameter capillary, quasi-monoenergetic bunches up to 300 MeV were observed. By detuning discharge delay from optimum guiding performance, self-trapping was found to be stabilized. For a 33 mm long, 300 mu m capillary, a parameter regime with high energy bunches, up to 1 Ge V, was found. In this regime, peak electron energy was correlated with the amount of trapped charge. Simulations show that bunches produced on a down-ramn and iniected into a channel-guided LWFA can produce stable beams with 0.2 MeV Ic-class momentum spread at high energies.
An Investigation of Laser-wakefield Acceleration in the Hydrogen-filled Capillary Discharge Waveguide
Author: Thomas P. A. IbbotsonPublisher:
ISBN:
Category : Laser-plasma interactions
Languages : en
Pages : 0
Book Description
This thesis describes a detailed investigation into the process of laser-wakefield acceleration (LWFA) for the generation of high-energy electron beams using the hydrogen-filled capillary discharge waveguide. In only the second experiment to be performed using the newly commissioned Astra-Gemini laser at the Rutherford Appleton Laboratory, electron beams were accelerated to energies greater than 0.5 GeV by laser pulses of energy 2.5J and peak power of 30T\~T. The injec- tion and acceleration of electron beams was seen to depend on the state of the plasma channel for axial electron densities less than 2.5 x 1018 cm -3. With the aid of simulations performed using the code WAKE it was found that the plasma channel allows the laser pulse to maintain its self-focussed spot size along the length of the capillary even below the critical power for self-guiding. It was found that the threshold laser energy required for the production of elec- tron beams was reduced by the use of an aperture placed early in the laser system. This was attributed to the increased energy contained in the central part of the focal spot of the laser. A short paper on this work was published in Physical Review Special Topics - Accelerators and Beams and a longer paper was published in the New Journal of Physics. Transverse interferometry was used to measure the electron density of the plasma channel used in the Astra-Gemini experiments. An imaging system was devised which used cylindrical optics to increase the field of view of the capillary longitudinally, whilst maintaining the trans- verse resolution. The measured properties were consistent with previous measurements made by Gonsalves et al. [J]. The observed longitudinal variations in the plasma channel parameters were not found to be significant enough to affect the injection process.
Challenges and Goals for Accelerators in the XXI Century
Author: Oliver BrningPublisher: World Scientific
ISBN: 9814436402
Category : Science
Languages : en
Pages : 855
Book Description
"The past 100 years of accelerator-based research have led the field from first insights into the structure of atoms to the development and confirmation of the Standard Model of physics. Accelerators have been a key tool in developing our understanding of the elementary particles and the forces that govern their interactions. This book describes the past 100 years of accelerator development with a special focus on the technological advancements in the field, the connection of the various accelerator projects to key developments and discoveries in the Standard Model, how accelerator technologies open the door to other applications in medicine and industry, and finally presents an outlook of future accelerator projects for the coming decades."--Provided by publisher.
Phase Space Dynamics in Plasma Based Wakefield Acceleration
Author: Xinlu XuPublisher: Springer Nature
ISBN: 9811523819
Category : Science
Languages : en
Pages : 138
Book Description
This book explores several key issues in beam phase space dynamics in plasma-based wakefield accelerators. It reveals the phase space dynamics of ionization-based injection methods by identifying two key phase mixing processes. Subsequently, the book proposes a two-color laser ionization injection scheme for generating high-quality beams, and assesses it using particle-in-cell (PIC) simulations. To eliminate emittance growth when the beam propagates between plasma accelerators and traditional accelerator components, a method using longitudinally tailored plasma structures as phase space matching components is proposed. Based on the aspects above, a preliminary design study on X-ray free-electron lasers driven by plasma accelerators is presented. Lastly, an important type of numerical noise—the numerical Cherenkov instabilities in particle-in-cell codes—is systematically studied.
Investigation of Staged Laser-Plasma Acceleration
Author: Satomi ShiraishiPublisher: Springer
ISBN: 3319085697
Category : Science
Languages : en
Pages : 133
Book Description
This thesis establishes an exciting new beginning for Laser Plasma Accelerators (LPAs) to further develop toward the next generation of compact high energy accelerators. Design, installation and commissioning of a new experimental setup at LBNL played an important role and are detailed through three critical components: e-beam production, reflection of laser pulses with a plasma mirror and large wake excitation below electron injection threshold. Pulses from a 40 TW peak power laser system were split into a 25 TW pulse and a 15 TW pulse. The first pulse was used for e-beam production in the first module and the second pulse was used for wake excitation in the second module to post-accelerate the e-beam. As a result, reliable e-beam production and efficient wake excitation necessary for the staged acceleration were independently demonstrated. These experiments have laid the foundation for future staging experiments at the 40 TW peak power level.
Controlling Electron Acceleration in Underdense and Overdense Laser-Plasma Interactions to Generate X-rays for Probing High Energy Density Material
Author: Kyle G MillerPublisher:
ISBN:
Category :
Languages : en
Pages : 251
Book Description
There is interest in using short-pulse x-rays that are small in source size, broad in energy spectrum, and high in photon number to probe and visualize the evolution of hot, dense material for both research and industrial applications. One method to produce such x-rays is to collide an energetic electron beam with a high-Z material, which will then emit bremsstrahlung radiation with many of the desired source characteristics. In this dissertation we study the physical processes of generating energetic electrons from laser-plasma interactions in both underdense and overdense plasmas. These laser-plasma interactions are nonlinear and kinetic in nature. Therefore, the particle-in-cell (PIC) algorithm is often the tool of choice for the simulations discussed within this dissertation, with length and time scales on the order of a millimeter and picosecond, respectively. Such simulations require the use of massively parallel computers. However, these simulations often suffer from having a large concentration of particles processed by relatively few computing elements, leading to decreases in performance due to a computational load imbalance. We present a dynamic load balancing technique for the PIC algorithm that effectively balances computational load across distributed-memory processes, in addition using a hybrid shared-memory scheme to increase scalability with shared-memory thread number by an order of magnitude and boost overall performance by a factor of two. Another useful PIC algorithm relevant to this work invokes a cylindrical geometry and azimuthal mode decomposition to yield proper three-dimensional geometric effects at the computational cost of a two-dimensional simulation. We also discuss improvements to this algorithm, where modifications to the particle initialization and field solver at the cylindrical axis eliminate spurious electromagnetic fields at the axis that have long been observed for this method. The second part of this dissertation explores the mechanism of direct laser acceleration (DLA) in laser-based plasma acceleration. This process occurs when the channel-guided laser fields overlap electrons either in the plasma wave wake or within an ion channel, and the frequency of the electron transverse motion matches the Doppler-shifted laser frequency. We first utilize the cylindrical mode decomposition to more accurately account for the energy gain from the DLA process compared to traditional methods, then show that laser wakefield accelerators (LWFAs) in both the self-modulated (SM-LWFA) and bubble regimes exhibit comparable contributions in energy from the wakefields and DLA process for the most energetic electrons. A customized finite-difference Maxwell field solver is then presented that corrects the dispersion relation of light in vacuum and removes a time-discretization error in the Lorentz force compared to the standard PIC algorithm. This solver is especially valuable when investigating DLA, and simulations using the customized solver demonstrate better agreement with experiment and with numerically integrated equations of motion. Single-particle motion is analyzed to study resonant motion in the DLA process, where electrons are observed to gain significant energy from laser fields but do not readily transition between different orders of resonance to gain further energy. We also simulate the motion of an electron probe beam propagating across an LWFA perpendicular to the laser propagation direction, which is timed with the laser pulse and measured far from the plasma to image the dynamics of the plasma wave wake. Although some qualitative agreement is observed between simulation and experiment, further investigation is needed to discern wakefield properties from the radiograph image alone. In the last part of this dissertation, we present simulations of laser-solid interactions to investigate the dynamics of energetic electron generation in the density upramp before an overdense plasma. These electrons propagate through the target and are then collided with a high-Z material to emit bremsstrahlung radiation. We first detail the requisite simulation techniques to correctly model this process, namely the splitting of energetic macro-particles to reduce enhanced wakefields, an extended particle absorber to prevent reflux at the boundary and a large transverse domain size to resolve long-wavelength magnetic field modes in the low- density plasma. A series of simulations are then carried out with varied laser amplitude and duration at constant energy to determine the laser configuration that yields the largest dose of few-MeV x-rays. We find that the high-amplitude laser pulses generate higher-temperature electron spectra, which in turn produce more x-rays at the desired energy. In addition, the shortest pulses generate many energetic electrons before the formation of self-generated magnetic fields, resulting in more directional beams of electrons and x-rays.