Acceleration of Laser-injected Electron Beams in an Electron-beam Driven Plasma Wakefield Accelerator PDF Download

Author: Alexander Knetsch
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Alexander Knetsch
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Karl Schmid
Publisher: Springer Science & Business Media
ISBN: 364219950X
Category : Science
Languages : en
Pages : 169

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This thesis covers the few-cycle laser-driven acceleration of electrons in a laser-generated plasma. This process, known as laser wakefield acceleration (LWFA), relies on strongly driven plasma waves for the generation of accelerating gradients in the vicinity of several 100 GV/m, a value four orders of magnitude larger than that attainable by conventional accelerators. This thesis demonstrates that laser pulses with an ultrashort duration of 8 fs and a peak power of 6 TW allow the production of electron energies up to 50 MeV via LWFA. The special properties of laser accelerated electron pulses, namely the ultrashort pulse duration, the high brilliance, and the high charge density, open up new possibilities in many applications of these electron beams.

Author: Oliver Brning
Publisher: World Scientific
ISBN: 9814436402
Category : Science
Languages : en
Pages : 855

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"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.

Author: Navid Vafaei-Najafabadi
Publisher:
ISBN:
Category :
Languages : en
Pages : 156

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A plasma wakefield accelerator (PWFA) uses a plasma wave (a wake) to accelerate electrons at a gradient that is three orders of magnitude higher than that of a conventional accelerator. When the plasma wave is driven by a high-density particle beam or a high-intensity laser pulse, it evolves into the nonlinear blowout regime, where the driver expels the background plasma electrons, resulting in an ion cavity forming behind the driver. This ion cavity has ideal properties for accelerating and focusing electrons. One method to insert electrons into this highly-relativistic, transient structure is by ionization injection. In this method, electrons resulting from further ionization of the ions inside the wake are trapped and accelerated by the wakefield. These injected electrons absorb the energy of the wake, resulting in a reduced accelerating field amplitude; this phenomenon is known as beam loading. This thesis discusses experiments that demonstrate how ionization injection can, on the one hand, lead to excessive beam loading and be a detriment to a PWFA, while on the other hand, it may be taken advantage of to produce bright electron beams that will be necessary for applications of a PWFA to a free electron laser (FEL) or a collider. These experiments were part of the FACET Campaign at the SLAC National Accelerator Laboratory and used FACET's 3 nC, 20.35 GeV electron beam to field ionize the plasma source and drive a wake. In the first experiment, the plasma source was a 30 cm column of rubidium (Rb) vapor. The low ionization potential and high atomic mass of Rb made it a suitable candidate as a plasma source for a PWFA. However, the low ionization potential of the Rb+ ion resulted in continuous ionization of Rb+ and injection of electrons along the length of the plasma. This resulted in heavy beam-loading, which reduced the strength of the accelerating field by half, making the Rb source unusable for a PWFA. In the second experiment, the plasma source was a column of lithium (Li) vapor bound by cold helium (He) gas. Here, the ionization injection of He electrons in the 10 cm boundary region between Li and He led to localized beam loading and resulted in an accelerated electron beam with high energy (32 GeV), a 10% energy spread, and an emittance an order of magnitude smaller than the drive beam. Particle-in-cell simulations indicate that the beam loading can be further optimized by reducing the injection region even more, which can lead to bright, high-current, low-energy-spread electron beams.

Author: Yunfeng Xi
Publisher:
ISBN:
Category :
Languages : en
Pages : 120

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Plasma-based acceleration, either driven by laser (LWFA) or driven by electron beam (PWFA) has the potential of accelerating electrons to GeV in a few cen- timeters. This allows construction of table-top accelerator which can be applied to build light source such as free electron laser (FEL) or high energy particle collider. The driver bunch loses energy to plasma when driving a wake. The following wit- ness bunch injected at correct phase will be accelerated. Here we report a novel injection scheme, laser-ionization injection where the witness bunch is formed by laser-ionizing higher-threshold gas such as He. Simulation and numerical calcula- tion is presented to evaluate the beam quality, the beam emittance is estimated to be 10 8 mrad. Experimental key issues such as timing synchronization of laser pulse and electron bunch and eliminate "dark current" are taken care of before the plasma acceleration experiment is carried out. Two beams are synchronized to 100-fs level via plasma radiation observation and Electro-Optic Sampling (EOS). "Dark current" is reduced to trivial level by tuning plasma density and driver bunch configuration. We observed 1 GeV gain of witness bunch with 5% energy spread.

Author: Xinlu Xu
Publisher: Springer Nature
ISBN: 9811523819
Category : Science
Languages : en
Pages : 138

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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.

Author: Jessica Shaw
Publisher:
ISBN:
Category :
Languages : en
Pages : 132

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In this dissertation, the direct laser acceleration (DLA) of ionization-injected electrons in a laser wakefield accelerator (LWFA) operating in the quasi-blowout regime has been investigated through experiment and simulation. In the blowout regime of LWFA, the radiation pressure of an intense laser pulse can push a majority of the plasma electrons out and around the main body of the pulse. The expelled plasma electrons feel the electrostatic field of the relatively-stationary ions and are thus attracted back towards the laser axis behind the laser pulse where they overshoot the axis and set up a wake oscillation. When ionization injection is used, the inner-shell electrons of higher-Z dopant atoms are tunnel ionized near the peak of the laser pulse. Those electrons slip back relative to the wake until they gain enough energy from the longitudinal wakefield to become trapped. Those electrons that are trapped off-axis will undergo betatron oscillations in response to the linear transverse focusing force of the ions. Through experiments and supporting simulations, this dissertation demonstrates that when there is a significant overlap between the drive laser and the trapped electrons in a LWFA cavity, the accelerating electrons can gain energy from the DLA mechanism in addition to LWFA. When laser pulse overlaps the trapped electrons, the betatron oscillations of the electrons in the plane of the laser polarization can lead to an energy transfer from the transverse electric field of the laser to the transverse momentum of the electrons. This enhanced transverse momentum can then be converted into increased longitudinal momentum via the v x B force of the laser. This process is known as DLA. In this experimental work, the properties of the electron beams produced in a LWFA where the electrons are injected by ionization injection and become trapped without escaping the laser field have been investigated. The maximum measured energy of the produced electron beams scales with the overlap between the electrons and the laser. Undispersed electrons beams are observed to be elliptical in the plane of the laser polarization, and the energy spectrum splits into a fork at higher energies when the electrons beams are dispersed orthogonal to the direction of the laser polarization. These characteristic features are reproduced in particle-in-cell (PIC) code simulations where particle tracking was used to demonstrate that such spectral features are signatures of the presence of DLA in LWFA. Further PIC simulations comparing LWFA with and without DLA show that the presence of DLA can lead to electron beams that have maximum energies that exceed the estimates given by the theory for the ideal blowout regime. The magnitude of the contribution of DLA to the energy gained by the electron was found to be on the order of the LWFA contribution. In the LWFAs studied here, both DLA and LWFA participate in accelerating the bulk of the electrons in the produced electron beam. The presence of DLA in a LWFA can also lead to enhanced betatron oscillation amplitudes and increased divergence in the direction of the laser polarization.

Author: Constantin Aniculaesei
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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This thesis describes experiments that explore the possibility of improving the quality of an electron beam obtained from a laser wakefield accelerator (LWFA) by shaping the longitudinal plasma density profile. Different density profiles have been obtained by employing a range of Laval nozzles with different geometries. These are modelled and numerically simulated under different conditions using Fluent 6.3. Density lineouts from simulations for different heights above the nozzle give the plasma density profile for each experimental condition. The plasma density profile is modified by changing the geometry of the nozzle, the interaction point, the laser beam angle relative to the exit plane of the nozzle and pressure of the gas. In this way the leading up-ramp length of the density profile (that interacts first with the laser) has been varied between 0.47 mm to 1.39 mm and the maximum plasma density varied between 1.29 x 1019 cm−3 to 2.03 x 1019 cm−3. The influence of the density profile parameters on the LWFA process is quantified by monitoring the properties of the generated electron beam. It is shown that the leading ramp of the plasma density profile i.e. the ramp that interacts first with the laser, has a strong influence on the quality of the electron beam. Density profiles with the same peak plasma density but different ramp lengths generate electron beams with a factor of 1.4 difference in charge, 1.1 in electron energy, 2 in pointing and 1.45 in energy spread. Longer ramp lengths enhance the quality of electron beams, which suggest that LWFA injection occurs at the entrance density ramp. Complex density profiles are produced by tilting the nozzle relative to the direction of propagation of the laser. This allows continuous tuning of the peak energy of the electron beam from 135 ± 2MeV up to 171 ± 2MeV. The electron beam energy spread show improvements from 20.7 ± 1.2% to 8.9 ± 0.9%. The charge closely follows the evolution of the energy spread and has a mean value of 0.61 ± 0.16 pC. Experimental results also show that the angular distribution of the electron beam becomes elliptical when the laser focal plane is moved from the edge of the gas jet towards the centre of the density profile. This result is linked to the existence of a distorted LWFA bubble that propagates off-axis therefore affecting the pointing and transverse shape of the electron beam.

Author: Mourou Gerard
Publisher: World Scientific
ISBN: 9811217149
Category : Science
Languages : en
Pages : 268

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Recent advancements in generation of intense X-ray laser ultrashort pulses open opportunities for particle acceleration in solid-state plasmas. Wakefield acceleration in crystals or carbon nanotubes shows promise of unmatched ultra-high accelerating gradients and possibility to shape the future of high energy physics colliders. This book summarizes the discussions of the 'Workshop on Beam Acceleration in Crystals and Nanostructures' (Fermilab, June 24-25 , 2019), presents next steps in theory and modeling and outlines major physics and technology challenges toward proof-of-principle demonstration experiments.