Characterisation Of A Laser Wakefield Accelerator With Ultra Short Probe Pulses

Author : Philip K. Franke
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (134 download)

DOWNLOAD NOW!

Download or read book Spatiotemporal Pulse Shaping for Laser-plasma-based Applications written by Philip K. Franke and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Laser produced plasma provides a basis for many emerging technologies because it can interact with photons and charged particles in powerful and unique ways. These laser-plasma-based applications frequently rely on the controlled coupling of the laser pulse to the plasma to achieve the desired effects. Spatiotemporal (ST) pulse shaping, referring to the intentional correlation of the spatial and temporal characteristics of the laser pulse, can enhance control over the laser-plasma coupling improving the utility of laser-plasma-based applications. This work presents the basic theory of two ST shaping techniques, the chromatic flying focus (CFF) [D.H. Froula et al., "Spatiotemporal control of laser intensity" Nature Photonics 12, 262?265 (2018), D.H. Froula et al., "Flying focus: Spatial and temporal control of intensity for laser-based applications" Physics of Plasmas 26] and the ultrashort flying focus (UFF) ["Dephasingless Laser Wakefield Acceleration" Physical Review Letters 124, 134802 (2020)], and explores their applications experimentally and theoretically. Both techniques have at least three advantages in common: 1) laser pulse focusing is cylindrically symmetric, allowing high focused intensities to be reached, 2) the focal range is decoupled from the spot size, allowing high intensity to be maintained over long distances, and 3) the intensity peak velocity (focal velocity, v f) is decoupled from the laser group velocity, facilitating intensity peaks with tunable velocity. CFF pulses derived from the Multi-Terawatt laser at the Laboratory for Laser Energetics were used to drive ionization waves of arbitrary velocity (IWAVs) in air. These IWAVs, which are the moving interface between a neutral medium and an ionized plasma, moved at the focal velocity v f when driven by low energy pulses with uniform power spectra, agreeing with theoretical predictions. Focal velocity ranges shown computationally to mitigate ionization refraction were also confirmed [D. Turnbull et al., "Ionization Waves of Arbitrary Velocity" Physical Review Letters 120, 225001 (2018), J.P. Palastro et al., "Ionization waves of arbitrary velocity driven by a flying focus" Physical Review A 97, 033835 (2018)]. Later experiments demonstrated IWAVs of large diameter using defocused laser pulses in a gas jet. The non-uniform power spectrum of these higher energy pulses resulted in experimentally observable changes to the IWAV diameter and trajectory. An analytic theory predicting the IWAV trajectory and diameter for CFF pulses with non-uniform power spectra was developed, and broadly agreed with the experimental observations. This theory was used to propose the use of power spectrum shaping as a way to better tune the IWAV characteristics [P. Franke et al., "Measurement and control of large diameter ionization waves of arbitrary velocity" Optics Express 27, 31978?31988 (2019)]. Photon acceleration, describing the continual frequency increase accrued by a photon in a time decreasing refractive index gradient as a means to generate extreme ultraviolet light, is an application shown computationally to be advanced by the generation of IWAVs. A computational investigation of three photon acceleration schemes enable by IWAVs is presented. A new optical shock-enhanced self-photon acceleration regime was identified using a finite-difference time-domain computational model. This regime, which is characterized by rapid spectral broadening and temporal compression of the drive laser pulse, could generate isolated attosecond pulses in the extreme ultraviolet with high efficiency [A.J. Howard et al., "Photon Acceleration in a Flying Focus" Physical Review Letters 123, 124801 (2019), P. Franke et al., "Optical shock-enhanced self-photon acceleration" Physical Review A 104, 043520 (2021)]. An experimental platform was developed to measure the UFF, and prototype radial echelon optics were manufactured. The echelon optics were fabricated using vapor-deposition through a rotating mask, and were measured to be suitable for initial experiments. An automated scanning spectral interferometer was built and benchmarked, then used to make initial measurements of the UFF. The UFF was not explicitly demonstrated, but several experimental shortcomings were identified, illuminating a path toward an ultimate demonstration. A successful demonstration of the UFF will immediately enable a series of experiments planned to study dephasingless laser wakefield acceleration and related topics"--Pages xi-xiii