STUDIES OF COHERENT FREE-ELECTRON LASERS DRIVEN BY COMPACT LINACS OR BY PLASMA WAKEFIELD ACCELERATORS
Tesi di Dottorato
Data di Pubblicazione:
2023
Citazione:
STUDIES OF COHERENT FREE-ELECTRON LASERS DRIVEN BY COMPACT LINACS OR BY PLASMA WAKEFIELD ACCELERATORS / M. Opromolla ; supervisor: V. Petrillo ; co-supervisor: G. Rossi ; director of the school: M. Paris. Università degli Studi di Milano, 2023 Jan 24. 35. ciclo, Anno Accademico 2022.
Abstract:
Free-Electron Lasers (FELs) constitute the last generation of synchrotron light sources: they are conventionally driven by a radio-frequency linear electron accelerator (LINAC), where the electron beam is accelerated to relativistic energies, followed by a chain of undulator magnets, which force the electron beam to oscillate and emit radiation. High brightness, tunable and transversely coherent radiation pulses with unique properties are finally delivered to the downstream experimental stations for a wide range of applications in the fields of physics, biology, medicine and chemistry.
External seeding techniques aimed at improving the intrinsically poor temporal coherence and shot-to-shot stability of a FEL starting from shot noise have been proposed and experimentally demonstrated.
State-of-the-art fully coherent FELs make use of an external coherent signal, which is basically a high-power laser system seeding and imprinting its coherence properties on the electrons at the undulator entrance, and exploit seeded schemes based on frequency up-conversion to increase the low frequency of the seed laser and generate fully coherent radiation at shorter wavelengths.
Independently of the specific seeded scheme, the output FEL radiation properties, such as wavelength and repetition rate, strongly depend on those of the seed laser.
In particular, the repetition rate capability of conventional high-power lasers is limited to few kHz at maximum, which is incompatible with the MHz-class ones of a superconducting LINAC, while their wavelength limits the minimum output wavelength that can be achieved with reasonable harmonic up-conversions: the study of alternative seeding sources and FEL configurations overcoming this limitation, thus exploiting the potentials of superconducting LINACs, is the new frontier of FEL science.
Such research line has synergies with another ambitious and innovative frontier of accelerator science, the study and development of plasma-based accelerators as well as advancements towards their application in light sources, whose ultimate goal is to make advanced radiation sources available to a wide range of users with the realisation of compact user facilities that could be built in small-scale laboratories.
\par This thesis deals with theoretical and numerical studies of novel schemes for a fully coherent FEL driven by a compact LINAC at high repetition rate or by a plasma-wakefield accelerator.
Coherent and high repetition rate FEL pulses would enable high resolution experiments and more data collection in shorter experimental times respectively, greatly improving the ongoing science at FELs by supporting new experiments.
In this scenario and in the framework of the MariX and BriXSinO projects in Milan, Italy, I investigated the FEL oscillator (FELO) configuration in different spectral regions from the THz down to the X-rays by means of a simulation code, written in Fortran, which iterates the required simulation steps for its study. \\
Based on the acquired knowledge of the FELO scheme, producing high-power coherent pulses suitable for FEL seeding, this thesis proposes two novel FEL oscillator-amplifier setups capable of generating high repetition rate and coherent radiation at short wavelengths in the tender X-ray range ($0.3-0.5$ nm).
In these two schemes, the seed pulses are provided by an Extreme-Ultra-Violet (EUV) FELO equipped with Molibdenum/Silicium multilayer mirrors and frequency up-conversion based on the electron beam phase space manipulation is performed.
The first proposed scheme, seeded by the EUV FELO, similarly to a fresh bunch High-Gain Harmonic Generation (HGHG) FEL scheme, is a three-stage harmonic FEL cascade made of different undulator sections, where the seed modulates the elect
Tipologia IRIS:
Tesi di dottorato
Elenco autori:
M. Opromolla
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