Controlling Electron Acceleration in Underdense and Overdense Laser-Plasma Interactions to Generate X-rays for Probing High Energy Density Material PDF Download
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Author: Kyle G Miller
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ISBN:
Category :
Languages : en
Pages : 251
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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.
Author: Kyle G Miller
Publisher:
ISBN:
Category :
Languages : en
Pages : 251
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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.
Author: Mianzhen Mo
Publisher:
ISBN:
Category : Electrons
Languages : en
Pages : 283
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Ultra-intense (> 10^18 W/cm^2) laser interaction with matter is capable of producing relativistic electrons which have a variety of applications in scientific and medical research. Knowledge of various aspects of these hot electrons is important in harnessing them for various applications. Of particular interest for this thesis is the investigation of hot electrons generated in the areas of Laser Wakefield Acceleration (LWFA) and Fast Ignition (FI). LWFA is a physical process in which electrons are accelerated by the strong longitudinal electrostatic fields that are formed inside the plasma cavities or wakes produced by the propagation of an ultra-intense laser pulse through an under-dense plasma. The accelerating E-fields inside the cavities are 1000 times higher than those of conventional particle accelerators and can accelerate electrons to the relativistic regime in a very short distance, on the order of a few millimeters. In addition, Betatron X-ray radiation can be produced from LWFA as a result of the transverse oscillations of the relativistic electrons inside the laser wakefield driven cavity. The pulse duration of Betatron radiation can be as short as a few femtoseconds, making it an ideal probe for measuring physical phenomena taking place on the time scale of femtoseconds. Experimental research on the electron acceleration of the LWFA has been conducted in this thesis and has led to the generation of mono-energetic electron bunches with peak energies ranging from a few hundreds of MeV to 1 GeV. In addition, the Betatron radiation emitted from LWFA was successfully characterized based on a technique of reflection off a grazing incidence mirror. Furthermore, we have developed a Betatron X-ray probe beamline based on the technique of K-shell absorption spectroscopy to directly measure the temporal evolution of the ionization states of warm dense aluminum. With this, we have achieved for the first time direct measurements of the ionization states of warm dense aluminum using Betatron X-ray radiation probing. Fast Ignition (FI) is an advanced scheme for inertial confinement fusion (ICF), in which the fuel ignition process is decoupled from its compression. Comparing with the conventional central hot-spot scheme for ICF, FI has the advantages of lower ignition threshold and higher gain. The success of FI relies on efficient energy coupling from the heating laser pulse to the hot electrons and subsequent transport of their energy to the compressed fuel. As a secondary part of this thesis, the transport of hot electrons in overdense plasma relevant to FI was studied. In particular, the effect of resistive layers within the target on the hot electron divergence and absorption was investigated. Experimental measurements were carried out and compared to simulations indicating minimal effect on the beam divergence but some attenuation through higher atomic number intermediate layers was observed.
Author: Joshua Joseph May
Publisher:
ISBN:
Category :
Languages : en
Pages : 250
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The continued development of the chirped pulse amplification technique has allowed for the development of lasers with powers of in excess of $10^{15}W$, for pulse lengths with durations of between .01 and 10 picoseconds, and which can be focused to energy densities greater than 100 giga-atmospheres. When such lasers are focused onto material targets, the possibility of creating particle beams with energy fluxes of comparable parameters arises. Such interactions have a number of theorized applications. For instance, in the Fast Ignition concept for Inertial Confinement Fusion \cite{Tabak:1994vx}, a high-intensity laser efficiently transfers its energy into an electron beam with an appropriate spectra which is then transported into a compressed target and initiate a fusion reaction. Another possible use is the so called Radiation Pressure Acceleration mechanism, in which a high-intensity, circularly polarized laser is used to create a mono-energetic ion beam which could then be used for medical imaging and treatment, among other applications. For this latter application, it is important that the laser energy is transferred to the ions and not to the electrons. However the physics of such high energy-density laser-matter interactions is highly kinetic and non-linear, and presently not fully understood. In this dissertation, we use the Particle-in-Cell code OSIRIS \cite{Fonseca:2002, Hemker:1999} to explore the generation and transport of relativistic particle beams created by high intensity lasers focused onto solid density matter at normal incidence. To explore the generation of relativistic electrons by such interactions, we use primarily one-dimensional (1D) and two-dimensional (2D), and a few three-dimensional simulations (3D). We initially examine the idealized case of normal incidence of relatively short, plane-wave lasers on flat, sharp interfaces. We find that in 1D the results are highly dependent on the initial temperature of the plasma, with significant absorption into relativistic electrons only possible when the temperature is high in the direction parallel to the electric field of the laser. In multi-dimensions, absorption into relativistic electrons arises independent of the initial temperature for both fixed and mobile ions, although the absorption is higher for mobile ions. In most cases however, absorption remains at $10's$ of percent, and as such a standing wave structure from the incoming and reflected wave is setup in front of the plasma surface. The peak momentum of the accelerated electrons is found to be $2 a_0 m_e c$, where $a_0 \equiv e A_0/m_e c^2$ is the normalized vector potential of the laser in vacuum, $e$ is the electron charge, $m_e$ is the electron mass, and $c$ is the speed of light. We consider cases for which $a_0>1$. We therefore call this the $2 a_0$ acceleration process. Using particle tracking, we identify the detailed physics behind the $2 a_0$ process and find it is related to the standing wave structure of the fields. We observe that the particles which gain energy do so by interacting with the laser electric field within a quarter wavelength of the surface where it is at an anti-node (it is a node at the surface). We find that only particles with high initial momentum -- in particular high transverse momentum -- are able to navigate through the laser magnetic field as its magnitude decreases in time each half laser cycle (it is an anti-node at the surface) to penetrate a quarter wavelength into the vacuum where the laser electric field is large. For a circularly polarized laser the magnetic field amplitude never decreases at the surface, instead its direction simply rotates. This prevents electrons from leaving the plasma and they therefore cannot gain energy from the electric field. For pulses with longer durations ($\gtrsim 250fs$), or for plasmas which do not have initially sharp interfaces, we discover that in addition to the $2 a_0$ acceleration at the surface, relativistic particles are also generated in an underdense region in front of the target. These particles have energies without a sharp upper bound. Although accelerating these particles removes energy from the incoming laser, and although the surface of the plasma does not stay perfectly flat and so the standing wave structure becomes modified, we find in most cases, the $2 a_0$ acceleration mechanism occurs similarly at the surface and that it still dominates the overall absorption of the laser. To explore the generation of relativistic electrons at a solid surface and transport of the heat flux of these electrons in cold or warm dense matter, we compare OSIRIS simulations with results from an experiment performed on the OMEGA laser system at the University of Rochester. In that experiment, a thin layer of gold placed on a slab of plastic is illuminated by an intense laser. A greater than order-of-magnitude decrease in the fluence of hot electrons is observed when those electrons are transported through a plasma created from a shock-heated plastic foam, as compared to transport through cold matter (unshocked plastic foam) at somewhat higher density. Our simulations indicate two reasons for the experimental result, both related to the magnetic field. The primary effect is the generation of a collimating B-field around the electron beam in the cold plastic foam, caused by the resistivity of the plastic. We use a Monte Carlo collision algorithm implemented in OSIRIS to model the experiment. The incoming relativistic electrons generate a return current. This generates a resistive electric field which then generates a magnetic field from Faraday's law. This magnetic field collimates the forward moving relativistic electrons. The collisionality of both the plastic and the gold are likely to be greater in the experiment than the 2D simulations where we used a lower density for the gold (to make the simulations possible) which heats up more. In addition, the use of 2D simulations also causes the plastic to heat up more than expected. We compensated for this by increasing the collisionality of the plasma in the simulations and this led to better agreement. The second effect is the growth of a strong, reflecting B-field at the edge of the plastic region in the shock heated material, created by the convective transport of this field back towards the beam source due to the neutralizing return current. Both effects appear to be caused primarily by the difference is density in the two cases. Owing to its higher heat capacity, the higher density material does not heat up as much from the heat flux coming from the gold, which leads to a larger resistivity. Lastly, we explored a numerical effect which has particular relevance to these simulations, due to their high energy and plasma densities. This effect is caused by the use of macro particles (which represent many real particles) which have the correct charge to mass ratio but higher charge. Therefore, any physics of a single charge that scales as $q^2/m$ will be artificially high. Physics that involves scales smaller than the macro-particle size can be mitigated through the use of finite size particles. However, for relativistic particles the spatial scale that matters is the skin depth and the cell sizes and particle sizes are both smaller than this. This allows the wakes created by these particles to be artificially high which causes them to slow down much faster than a single electron. We studied this macro-particle stopping power theoretically and in OSIRIS simulations. We also proposed a solution in which particles are split in to smaller particles as they gain energy. We call this effect Macro Particle Stopping. Although this effect can be mitigated by using more particles, this is not always computationally efficient. We show how it can also be mitigated by using high-order particle shapes, and/or by using a particle-splitting method which reduces the charge of only the most energetic electrons.
Author: Dean Richard Rusby
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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In recent years, high intensity laser-matter interactions (> 1018 W/cm2) have been shown to produce bright, compact sources of many different particles. These include x-rays, neutrons, protons and electrons, which can be used in applications such as x-ray and electron radiography. The potential use of these sources for industrial applications is promising. However, the scalability and tuning of the sources needs to be understood at a fundamental level. This thesis reports on three aspects of the development and application of these sources; the first two discuss applications of laser-plasma interactions. Firstly, the generation, characterisation and tunability of high-energy x-rays (= 200 keV) produced by the hot-electrons generated inside a solid target for the application of x-ray radiography. The characterisation of the x-ray source is conducted using a novel scintillator based absorption spectrometer. This source of x-rays was then used to radiograph a high density test object. Secondly, a novel technique of x-ray backscatter is investigated numerically and demonstrated experimentally for the first time on a laser facility. This uses the high energy electrons generated via wakefield acceleration to probe deeper into materials than traditional backscatter techniques. Finally, an investigation is reported examining the fundamental dynamics of electrons escaping from solid targets under different irradiation conditions. Experimentally, the number of escaping electrons was shown to maximise for certain laser illumination conditions; this was also explored using PIC simulations. The new results discussed in these three sections produce important new understanding of laser-driven x-ray generation and its application to penetrative probing and imaging for possible future industrial applications as well as the understanding of escaping electron dynamics.
Author: Jonathan Lee Peebles
Publisher:
ISBN:
Category :
Languages : en
Pages : 248
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Relativistic laser plasma interactions in conjunction with an underdense pre-plasma have been shown to generate a two temperature component electron spectrum. The lower temperature component described by "ponderomotive scaling" is relatively well known and understood and is useful for applications such as the fast ignition inertial confinement fusion scheme. The higher energy electrons generated due to pre-plasma are denoted as "super-ponderomotive" electrons and facilitate interesting and useful applications. These include but are not limited to table top particle acceleration and generating high energy protons, x-rays and neutrons from secondary interactions. This dissertation describes experimental and particle-in-cell computational studies of the electron spectra produced from interactions between short pulse high intensity lasers and controlled pre-plasma conditions. Experiments were conducted at 3 laser labs: Texas Petawatt (University of Texas at Austin), Titan (Lawrence Livermore National Laboratory) and OMEGA-EP (University of Rochester). These lasers have different capabilities, and multiple experiments were carried out in order to fully understand super-ponderomotive electron generation and transport in the high intensity laser regime (I > 10^18 W/cm^2). In these experiments, an additional secondary long pulse beam was used to generate different scale lengths of "injected" pre-plasma while the pulse length and intensity of the short pulse beam were varied. The temperature and quantity of super-ponderomotive electrons were monitored with magnetic spectrometers and inferred via bremsstrahlung spectrometers while trajectory was estimated via Cu-K[alpha] imaging. The experimental and simulation data show that super-ponderomotive electrons require pulse lengths of at least 450 fs to be accelerated and that higher intensity interactions generate large magnetic fields which cause severe deflection of the super-ponderomotive electrons. Laser incidence angle is shown to be extremely important in determining hot electron trajectory. Longer pulse length data taken on OMEGA-EP and Titan showed that super-ponderomotive electrons could be created without the need for an initial pre-plasma due to the underdense plasma created during the high intensity interaction alone.
Author:
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ISBN:
Category :
Languages : en
Pages : 5
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An experiment investigating the production of relativistic electrons from the interaction of ultrashort multi-terawatt laser pulses with an underdense plasma is presented. Electrons were accelerated to tens of MeV and the maximum electron energy increased as the plasma density decreased. Simulations have been performed in order to model the experiment. They show a good agreement with the trends observed in the experiment and the spectra of accelerated electrons could be reproduced successfully. The simulations have been used to study the relative contribution of the different acceleration mechanisms: plasma wave acceleration, direct laser acceleration and stochastic heating. The results show that in low density case (1 percent of the critical density) acceleration by laser is dominant mechanism. The simulations at high density also suggest that direct laser acceleration is more efficient that stochastic heating.
Author:
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ISBN:
Category :
Languages : en
Pages : 11
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Collisionally pumped soft x-ray lasers now operate over a wavelength range extending from 4-40 nm. With the recent advances in the development of multilayer mirrors and beamsplitters in the soft x-ray regime, the authors can utilize the unique properties of x-ray lasers to study large, rapidly evolving laser-driven plasmas with high electron densities. Using a neon-like yttrium x-ray laser which operates at a wavelength of 15.5 nm, they have performed a series of x-ray laser interferometry experiments to characterize plasmas relevant to inertial confinement fusion. In this paper the authors describe experiments using a soft x-ray laser interferometer, operated in the Mach-Zehnder configuration, to study CH plasmas and exploding foil targets commonly used for x-ray laser targets. The two-dimensional density profiles obtained from the interferograms allow the authors to validate and benchmark their numerical models used to study the physics of laser-plasma interactions.
Author:
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Category : Controlled fusion
Languages : en
Pages : 142
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Author: Brian Henry Shaw
Publisher:
ISBN:
Category :
Languages : en
Pages : 111
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For over 10 years, laser plasma acceleration (LPA) has been a rapidly growing technology used to create electron beams on length-scales much smaller than that of a conventional RF-accelerator [1]. As electron beam properties improve, research for LPAs is expanding to take advantage of the creation and accessibility of high-quality electron beams from plasma targets. Two applications which are currently being explored are a multi-stage plasma accelerator to reach energies greater than those a single-stage accelerator can achieve and exploring the possibility of an LPA based free-electron laser (FEL) light source. Research supporting both of these efforts has been performed on the 50 TW TREX laser system at the BELLA Center at the Lawrence Berkeley National Lab, and the results of these efforts are described in this dissertation. Using chirped-pulsed amplification to produce high-quality laser pulses up to petawatt levels, experimental results have yielded laser driven electron beam energies up to 4.25 GeV [2]. By tuning the density of the target, the accelerating gradients sustained by the plasma can grow beyond 100 GeV/m [3] (10^3 times larger than that of a conventional RF accelerator). However, limiting factors such as dephasing of the electron beam from the plasma wake, defocusing of a laser pulse, and energy depletion of the laser into the plasma limit the maximum sensible length of a plasma accelerator. Staging the LPA with two or more accelerating modules could be the next step towards producing beams with energies greater than those possible with a single stage. One requirement for staged acceleration is that the laser pulse used to drive the first accelerating stage must be coupled out of the beamline, and a fresh laser pulse must be coupled in for the second stage to post accelerate the electrons. To do this while maintaining a short scale length between the two stages requires an optic to be placed near the final focus of the second laser pulse. Because damage will occur when the laser pulse interacts with a steering optic near focus, the coupling optic must be capable of replacing the surface following damage on each successive shot. This thesis comprises a detailed investigation of the physics of using a plasma mirror (PM) from a tape by reflecting ultrashort pulses from a laser-triggered surface plasma. The tapes used in the characterization of the PM are VHS and computer data storage tape. The tapes are 6.6 m (computer storage tape) and 15 m (VHS) thick. Each tape is 0.5 inches wide, and 10s of meters of tape are spooled using a tape drive; providing thousands of shots on a single reel of tape. The amount of reflected energy of the PM was studied for different input intensities. The fluence was varied by translating the focus of the laser upstream and downstream of the tape, which changed the spot size on the tape surface and hence changed the fluence. This study measured reflectances from both sides of the two tapes, and for input light of both s and p-polarizations. Lastly, an analytic model was developed to understand the reflectance as a function of fluence for each tape material and polarization. Another application that benefits from the advancements of LPA technology is an LPAbased FEL. By sending a high quality electron bunch through an undulator (a periodic structure of positive and negative magnetic poles), the electrons oscillate transversely to the propagation axis and produce radiation. The 1.5 m THUNDER undulator [4] at the BELLA Center has been commissioned using electron beams of 400MeV beams with broad energy spread (35%) [5]. To produce a coherent LPA-based FEL, the beam quality would need to improve to sub-percent level energy spread. A seed source could be used to help induce bunching of the electron beam within the undulator. This thesis described the experimental investigation of the physics of using solid-based surface high-harmonic generation (SHHG) from a thin tape as a possible seed source for an FEL. A thin tape placed within centimeters of the undulator's entrance could act as a harmonic generating source, while simultaneously transmitting an electron beam. This removes the need for transport optics for the XUV photons and the need for additional optics to overlap the seed beam with the electron beam at the undulator entrance. By operating at sub-relativistic laser strengths, harmonics up to the 17th order of 800 nm light are produced using an SHHG technique known as coherent wake emission (CWE). CWE pulse properties such as divergence, energy, conversion efficiency, and spectrum are measured for a wide range of tape materials and drive laser conditions. A clear correlation between surface roughness and harmonic beam divergence is found. The measured pulse properties for the 15th harmonic from VHS tape (conversion efficiency 6.5x10^-7 and an rms divergence of 12 mrad), the 100 mJ-level, 40-50 fs-class drive laser, produces peak powers of several MW's of XUV pulses. The results of a 1D model indicate that these CWE pulses with MW level powers are sufficient for seed-induced FEL gain.
Author: Evan Stuart Dodd
Publisher:
ISBN:
Category :
Languages : en
Pages : 334
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