Modern science advancements rely on the possibility of producing short laser-like coherent pulses in the XUV and in the X-rays wavelength ranges to probe electronic structure in atoms, molecules and solid-state matter. For this reason, light-sources including synchrotrons, inverse Compton scattering, high harmonic generation in gas (HHG) and free electron lasers (FELs) are invaluable tools for research in these fields. In particular, they all have in common the exploitation of the radiating process resulting from electrons’ acceleration under the influence of an electromagnetic field. The aim of this thesis is to explore the impact of electrons’ dynamics on the coherence of FELs seeded by an external laser. In this thesis I demonstrate that electrons’ dynamics plays a major role in the conversion and transformation of light’s features, such as coherence, which can be transmitted to electrons and "inherited" from the re-emitted light. To fulfill this purpose, both the theoretical and the experimental approaches have been used. Most of the models presented, derived or extended in this work are, in fact, supported by experimental evidence. The interplay between electrons and light’s properties is investigated using both classical and quantum dynamics. While the former is routinely adopted to describe the FEL dynamics and collective phenomena in an electron bunch, the latter becomes mandatory to fully achieve a faithful description of the varieties of phenomena that involve the emission of photons. From the classical point of view, a comprehensive analytical model for electron beam longitudinal dynamics is derived by including a new phenomenon, known as intrabeam scattering, and by investigating its effect on the electrons’ distribution. The predictions of this model can be directly compared with both beam and FEL measurements, showing a good agreement with both. From the quantum-dynamical point of view, we start to explore the possibility to answer the following question: "is it possible to introduce quantum features, such as coherence, in any process of harmonic generation from a coherent light pulse?" In order to do so, we focus our attention on the characterization of quantum coherence via photon number distribution and the quantum electrodynamics of an electron in a laser field. The practical aspect of my investigation is threefold: the prediction and characterization of electron beam quality; the optimization of seeded and unseeded FELs performances, that is possible through the mitigation of instabilities originated in the electron bunch; the investigation of unexplored FELs features and configurations that could be exploited for novel experiments. Finally, although the results and discussions are directly applied to the FEL case, some of the theoretical results regarding the coherence can be applied, without loss of generality, to any process of electrons-light interaction.

Modern science advancements rely on the possibility of producing short laser-like coherent pulses in the XUV and in the X-rays wavelength ranges to probe electronic structure in atoms, molecules and solid-state matter. For this reason, light-sources including synchrotrons, inverse Compton scattering, high harmonic generation in gas (HHG) and free electron lasers (FELs) are invaluable tools for research in these fields. In particular, they all have in common the exploitation of the radiating process resulting from electrons’ acceleration under the influence of an electromagnetic field. The aim of this thesis is to explore the impact of electrons’ dynamics on the coherence of FELs seeded by an external laser. In this thesis I demonstrate that electrons’ dynamics plays a major role in the conversion and transformation of light’s features, such as coherence, which can be transmitted to electrons and "inherited" from the re-emitted light. To fulfill this purpose, both the theoretical and the experimental approaches have been used. Most of the models presented, derived or extended in this work are, in fact, supported by experimental evidence. The interplay between electrons and light’s properties is investigated using both classical and quantum dynamics. While the former is routinely adopted to describe the FEL dynamics and collective phenomena in an electron bunch, the latter becomes mandatory to fully achieve a faithful description of the varieties of phenomena that involve the emission of photons. From the classical point of view, a comprehensive analytical model for electron beam longitudinal dynamics is derived by including a new phenomenon, known as intrabeam scattering, and by investigating its effect on the electrons’ distribution. The predictions of this model can be directly compared with both beam and FEL measurements, showing a good agreement with both. From the quantum-dynamical point of view, we start to explore the possibility to answer the following question: "is it possible to introduce quantum features, such as coherence, in any process of harmonic generation from a coherent light pulse?" In order to do so, we focus our attention on the characterization of quantum coherence via photon number distribution and the quantum electrodynamics of an electron in a laser field. The practical aspect of my investigation is threefold: the prediction and characterization of electron beam quality; the optimization of seeded and unseeded FELs performances, that is possible through the mitigation of instabilities originated in the electron bunch; the investigation of unexplored FELs features and configurations that could be exploited for novel experiments. Finally, although the results and discussions are directly applied to the FEL case, some of the theoretical results regarding the coherence can be applied, without loss of generality, to any process of electrons-light interaction.

Impact of the Electrons Dynamics on the Free-electron Lasers Radiation Coherence / Perosa, Giovanni. - (2023 Feb 22).

Impact of the Electrons Dynamics on the Free-electron Lasers Radiation Coherence

PEROSA, GIOVANNI
2023-02-22

Abstract

Modern science advancements rely on the possibility of producing short laser-like coherent pulses in the XUV and in the X-rays wavelength ranges to probe electronic structure in atoms, molecules and solid-state matter. For this reason, light-sources including synchrotrons, inverse Compton scattering, high harmonic generation in gas (HHG) and free electron lasers (FELs) are invaluable tools for research in these fields. In particular, they all have in common the exploitation of the radiating process resulting from electrons’ acceleration under the influence of an electromagnetic field. The aim of this thesis is to explore the impact of electrons’ dynamics on the coherence of FELs seeded by an external laser. In this thesis I demonstrate that electrons’ dynamics plays a major role in the conversion and transformation of light’s features, such as coherence, which can be transmitted to electrons and "inherited" from the re-emitted light. To fulfill this purpose, both the theoretical and the experimental approaches have been used. Most of the models presented, derived or extended in this work are, in fact, supported by experimental evidence. The interplay between electrons and light’s properties is investigated using both classical and quantum dynamics. While the former is routinely adopted to describe the FEL dynamics and collective phenomena in an electron bunch, the latter becomes mandatory to fully achieve a faithful description of the varieties of phenomena that involve the emission of photons. From the classical point of view, a comprehensive analytical model for electron beam longitudinal dynamics is derived by including a new phenomenon, known as intrabeam scattering, and by investigating its effect on the electrons’ distribution. The predictions of this model can be directly compared with both beam and FEL measurements, showing a good agreement with both. From the quantum-dynamical point of view, we start to explore the possibility to answer the following question: "is it possible to introduce quantum features, such as coherence, in any process of harmonic generation from a coherent light pulse?" In order to do so, we focus our attention on the characterization of quantum coherence via photon number distribution and the quantum electrodynamics of an electron in a laser field. The practical aspect of my investigation is threefold: the prediction and characterization of electron beam quality; the optimization of seeded and unseeded FELs performances, that is possible through the mitigation of instabilities originated in the electron bunch; the investigation of unexplored FELs features and configurations that could be exploited for novel experiments. Finally, although the results and discussions are directly applied to the FEL case, some of the theoretical results regarding the coherence can be applied, without loss of generality, to any process of electrons-light interaction.
22-feb-2023
DI MITRI, SIMONE
35
2021/2022
Settore FIS/03 - Fisica della Materia
Università degli Studi di Trieste
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/3041022
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