X-ray radiation from relativistic charged particle beams has nowadays achieved unprecedented high brilliance and high degree of coherence, fostering the development of coherence-based techniques such as coherent diffractive imaging, photon correlation spectroscopy and phase contrast imaging. Probing the spatial and temporal coherence properties of the X-ray beam is of outermost importance for proper planning of the experiments and for unbiased data reduction. It also paves the way to non-invasive diagnostics techniques aimed at gauging the transverse emittance of the particle beam. Consequently, coherence diagnostics of the radiation emitted in third- and fourth-generation light sources represents an increasingly challenging demand. In this thesis we describe a novel coherence diagnostics technique named Heterodyne Near Field Speckle (HNFS). It exploits the staggering self-referenced interference between the weak spherical waves scattered by nanoparticles in a colloidal suspension and the strong transmitted field to probe the coherence properties of the radiation by means of Fourier analysis of the resulting stochastic speckle fields. A criterion based on master curves from data acquired at different sample-detector distances is introduced, allowing to gauge spatial and temporal coherence separately by means of two different scaling laws. The technique requires a minimal setup and it is ultimately wavelength independent. It can be operated also at X-ray wavelengths, remarkably without any dedicated optics. We first show results obtained with visible table-top thermal sources, validating the master curve criterion and introducing the concept of Analogical Optical Modeling. Then we provide a characterization of the spatio-temporal coherence properties of a pulsed High Harmonic Generation laser at the ELETTRA synchrotron (Trieste, Italy). Finally, the technique is applied to measure the coherence properties of visible synchrotron radiation and of soft X-ray undulator radiation at the ALBA facility (Barcelona, Spain), showing how the technique can be effectively implemented as a valuable beam diagnostics tool.
DIAGNOSTICS OF PARTIALLY COHERENT RADIATION FROM ULTRARELATIVISTIC BEAMS: THE HETERODYNE NEAR FIELD SPECKLE APPROACH / M. Siano ; tutor: M. A. C. Potenza; supervisore: B. Paroli. DIPARTIMENTO DI FISICA, 2017 Dec 19. 30. ciclo, Anno Accademico 2017. [10.13130/m-siano_phd2017-12-19].
DIAGNOSTICS OF PARTIALLY COHERENT RADIATION FROM ULTRARELATIVISTIC BEAMS: THE HETERODYNE NEAR FIELD SPECKLE APPROACH
M. Siano
2017
Abstract
X-ray radiation from relativistic charged particle beams has nowadays achieved unprecedented high brilliance and high degree of coherence, fostering the development of coherence-based techniques such as coherent diffractive imaging, photon correlation spectroscopy and phase contrast imaging. Probing the spatial and temporal coherence properties of the X-ray beam is of outermost importance for proper planning of the experiments and for unbiased data reduction. It also paves the way to non-invasive diagnostics techniques aimed at gauging the transverse emittance of the particle beam. Consequently, coherence diagnostics of the radiation emitted in third- and fourth-generation light sources represents an increasingly challenging demand. In this thesis we describe a novel coherence diagnostics technique named Heterodyne Near Field Speckle (HNFS). It exploits the staggering self-referenced interference between the weak spherical waves scattered by nanoparticles in a colloidal suspension and the strong transmitted field to probe the coherence properties of the radiation by means of Fourier analysis of the resulting stochastic speckle fields. A criterion based on master curves from data acquired at different sample-detector distances is introduced, allowing to gauge spatial and temporal coherence separately by means of two different scaling laws. The technique requires a minimal setup and it is ultimately wavelength independent. It can be operated also at X-ray wavelengths, remarkably without any dedicated optics. We first show results obtained with visible table-top thermal sources, validating the master curve criterion and introducing the concept of Analogical Optical Modeling. Then we provide a characterization of the spatio-temporal coherence properties of a pulsed High Harmonic Generation laser at the ELETTRA synchrotron (Trieste, Italy). Finally, the technique is applied to measure the coherence properties of visible synchrotron radiation and of soft X-ray undulator radiation at the ALBA facility (Barcelona, Spain), showing how the technique can be effectively implemented as a valuable beam diagnostics tool.File | Dimensione | Formato | |
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phd_unimi_R11028.pdf
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