This thesis shows the characterization of the plasma sources needed for the plasma-based experiments of SPARC_LAB. During this thesis work, I have studied and implemented the tools needed to measure the plasma density into both gas-filled and laser trigger ablative capillaries. The diagnostic system, based on the analysis of the Stark broadening of the emitted spectral lines, allowed to measure in a single shot the evolution of the plasma density variation along the entire capillary length in steps of 100 ns. As far as we know, this is the first single-shot, longitudinally-resolved measurement based on the Stark broadening analysis to measure low density plasma evolution (10^17 cm^-3) in a capillary discharge. By knowing the temporal evolution of the plasma density, it is possible to chose the correct working point for the accelerator and to check its stability and reliability. Moreover, the versatility of the system allows to verify online the proper functioning of the acceleration process, monitoring the variation of plasma density distribution along the acceleration path. This system has been implemented in the SPARC bunker and it has been used to characterize hydrogen filled capillary discharge. To complete the characterization of these capillaries, the discharge current profile has been characterized. The same diagnostic tool has been used to study how to proper engineering of the longitudinal plasma density can be performed with 3D printed laser trigger ablative capillaries whose prototyping cost is negligible, thanks to relatively fast manufacturing processes and their cheap materials. This investigation leads to measure the effect of the tapering of the capillary on the plasma density distribution along the whole capillary length. Tailoring the density from the beginning to the end of the interaction let to preserve the beam quality after the acceleration, but also it ensures the matching between the beams and the plasma. Finally, I implemented a Mach-Zehnder interferometer to detect the plasma density along the propagation length of a laser pulse in a gas-jet for self injection LWFA experiments performed at SPARC_LAB.

Plasma source characterization for plasma-based acceleration experiments / Filippi, Francesco. - (2017 Feb 21).

Plasma source characterization for plasma-based acceleration experiments

FILIPPI, FRANCESCO
21/02/2017

Abstract

This thesis shows the characterization of the plasma sources needed for the plasma-based experiments of SPARC_LAB. During this thesis work, I have studied and implemented the tools needed to measure the plasma density into both gas-filled and laser trigger ablative capillaries. The diagnostic system, based on the analysis of the Stark broadening of the emitted spectral lines, allowed to measure in a single shot the evolution of the plasma density variation along the entire capillary length in steps of 100 ns. As far as we know, this is the first single-shot, longitudinally-resolved measurement based on the Stark broadening analysis to measure low density plasma evolution (10^17 cm^-3) in a capillary discharge. By knowing the temporal evolution of the plasma density, it is possible to chose the correct working point for the accelerator and to check its stability and reliability. Moreover, the versatility of the system allows to verify online the proper functioning of the acceleration process, monitoring the variation of plasma density distribution along the acceleration path. This system has been implemented in the SPARC bunker and it has been used to characterize hydrogen filled capillary discharge. To complete the characterization of these capillaries, the discharge current profile has been characterized. The same diagnostic tool has been used to study how to proper engineering of the longitudinal plasma density can be performed with 3D printed laser trigger ablative capillaries whose prototyping cost is negligible, thanks to relatively fast manufacturing processes and their cheap materials. This investigation leads to measure the effect of the tapering of the capillary on the plasma density distribution along the whole capillary length. Tailoring the density from the beginning to the end of the interaction let to preserve the beam quality after the acceleration, but also it ensures the matching between the beams and the plasma. Finally, I implemented a Mach-Zehnder interferometer to detect the plasma density along the propagation length of a laser pulse in a gas-jet for self injection LWFA experiments performed at SPARC_LAB.
21-feb-2017
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1102637
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