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Ultimo aggiornamento 24 lug 2012
Autore
 Naveen Chandra Pathak
Sesso M
Esperimento NTA-PLASMONX
Tipo Dottorato
Destinazione dopo il cons. del titolo
Università Università Di Pisa
Strutt.INFN/Ente
 Lab. Naz. di Frascati
Titolo Laser Pulse Propagation in Plasmas and its implication on frequency up-shift and electron acceleration
Abstract Abstract This thesis documents the study of elementary processes in interaction of intense, ultrashort laser pulses with underdense plasmas. Main objective of this thesis is to understand the basic phenomena resulting from the interaction of ultra-short ultra-intense laser pulses with matter and to study the mechanism which eventually leads to generation of high energetic electrons, in laser based plasma accelerators. In a broad prospective, the work here can be described as a detailed experimental and numerical study of laser matter interaction, plasma formation and acceleration of particles. The motivation for these experiments arises from the fact that the results are relevant from both fundamental and applied research point of view. The light matter interaction is basically associated with the behaviour of individual atom exposed to high fields. The knowledge of this behaviour is important, as the basic interaction mechanism between laser and matter eventually drives the overall physical mechanism of the investigated phenomena. For this purpose numerical simulation based on optical field ionization was developed. These calculations yield information about the plasma density distribution within a given experimental conditions. The knowledge of the electron density distribution and its dynamics is very useful in interpretingmany observed phenomena during the experiment. When working with short pulse laser systems, possible pre-pulses that precedes the main pulse have to be taken into account. The numerical study on ionization is further extended for the inclusion of the pre-pulse effect in high intense pulses. One of the important feature during the experimental work is the use of time domain interferometry. This allowed to freeze the dynamics of the electron density evolution on femtosecond time scales up to several picoseconds. This was done by taking the snapshots of the process initiated by the main laser pulse by another pulse (called probe pulse) in terms of fringe shift. With ultrashort and high intense laser pulses the physical behaviour of the medium changes drastically in a time comparable or shorter than the pulse duration. This ultrafast change in the physical properties of the medium induces spatial and spectral modification in the propagating laser pulses. Study of these modifications could enhance the understanding ii of how intense optical pulses propagates in plasmas. Search for stable propagation of intense laser pulses in underdense plasmas and study of their spectrum modification was one of the most important work during the experiments. High energetic electrons with good bunch parameters have been successfully generated during the first phase of the experiment at LNF, with the newly built FLAME laser system. The main objective of the new facility at LNF is to push the electron energy to GeV scale and to find ways for new compact radiation sources. The present work is motivated by the need to gain understanding of laser pulse propagation in plasmas and its implications on electron acceleration by high-intensity laser irradiation of gas targets and their application. The results, in particular the frequency shift of the laser pulse, have taken a further step towards a broad application of laser gas interaction in a large variety of fields like accelerator physics and supercontinuum generation.
Anno iscrizione
Data conseguimento 24 giu 2011
Luogo conseguimento Pisa
Relatore/i
 Danilo Giulietti   
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Thesis_21April.pdf
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