Frequency Domain Holography of laser wakefields
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In this dissertation, single-shot measurement of longitudinal and transverse structure of resonantly driven laser wakefields by Frequency Domain Holography (FDH) is demonstrated. Visualization of laser wakefield structure is crucial for understanding the complex dynamics of the mutual interaction between the driving pulse, wake- field density oscillations and accelerated electron bunch. This diagnostic therefor provides a necessary tool for researchers to learn how to control and fine tune the interaction to produce electron beams with desirable properties. Wakefields were measured in a 2 mm Helium gas jet, for electron densities between 1 x 1018 and 6 x 1018 cm−3 , and laser pulses of 30 fs duration and peak powers between 10 TW and 30 TW. Detailed structural features of the wakefields, including radial extent of the wake, longitudinal wake development, and wavefront curvature, as well as features of the accompanying ionization front and plasma column are resolved. Results are compared with PIC simulations, and show a high degree of correspondence. Weaknesses of the current implementation of the technique and extensions to other parameter regimes are discussed.