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Tilted snowplow electron acceleration with simultaneously spatially and temporally focused laser pulses
Wilhelm, Alex Matthew
Wilhelm, Alex Matthew
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2021
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2023-04-14
Abstract
Advances in high power laser technology have enabled a new generation of laser driven particle accelerator technologies. These accelerators offer unique benefits such as larger acceleration gradients or higher repetition rates over conventional radio frequency acceleration methods. In this thesis I demonstrate both analytically and numerically a novel laser driven ponderomotive acceleration scheme for accelerating electrons in free space. The technique exploits the pulse front tilt (PFT) of simultaneously spatially and temporally focused (SSTF) laser pulses to reduce the pulse’s interaction speed with the electrons to below the vacuum speed of light. The reduction in the pulse front velocity allows electrons to be captured and accelerated sideways, like snow on a snowplow, by the ponderomotive force of the intense laser pulse. The analytic scaling laws of tilted snowplow ponderomotive acceleration are derived, and single particle simulations are performed to verify the basic scheme. In addition, a model of SSTF pulse propagation is implemented in the particle-in-cell (PIC) code OSIRIS 4.0 and used to study collective dynamics of the acceleration scheme. To study the dynamic evolution of the SSTF pulse, a novel version of the dispersion scan pulse characterization technique is demonstrated which can measure the temporal profile of the SSTF pulse at any longitudinal position in the focus and characterizes the angular chirp. This method is combined with a novel, improved phase retrieval algorithm for dispersion scan which uniquely determines the correct sign of the retrieved field through the application of Newton’s method. Additional work demonstrates a nonlinear optical process where photon spin can be converted to photon orbital angular momentum through second harmonic generation in underdense plasmas. This helps illuminate the fundamental nature of the angular momentum of light and its interaction with ordinary matter.
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