High resolution multielement XRF spectroscopy of extended and diffused sources with a graphite mosaic crystal based Von Hamos spectrometer

High resolution Bragg spectroscopy from millimetric size sources has been performed in 6–20 keV range with the VOXES HAPG spectrometer.

Gaseous Bose–Einstein condensates

The (gaseous) BECs are introduced: clouds of 106−8 alkali metal atoms, usually 87Rb or 23Na, below ~1 μ‎K. The laser cooling and magnetic trapping are described including the evaporation step needed to reach the conditions for condensation. The magnetooptical and Ioffe–Pritchard traps are described. Imaging methods, both destructive and non-destructive are described. Evidence of condensation is presented; and of interference between separated clouds, thus confirming the coherence of the condensates. The measurement of the condensate fraction is recounted. The Gross–Pitaevskii analysis of condensate properties is given in an appendix. How Bragg spectroscopy is used to obtain the dispersion relation for excitations is detailed. Finally the BEC/BCS crossover is introduced and the role therein of Feshbach resonances.

Pyrolitic Graphite Mosaic Crystal Thickness and Mosaicity Optimization for an Extended Source Von Hamos X-ray Spectrometer

Bragg spectroscopy, one of the best established experimental techniques for high energy resolution X-ray measurements, has always been limited to the measurement of photons produced from well collimated (tens of microns) or point-like sources; recently, the VOXES collaboration at INFN National Laboratories of Frascati developed a prototype of a high resolution and high precision X-ray spectrometer working also with extended isotropic sources. The realized spectrometer makes use of Highly Annealed Pyrolitic Graphite (HAPG) crystals in a “semi”-Von Hamos configuration, in which the position detector is rotated with respect to the standard Von Hamos one, to increase the dynamic energy range, and shows energy resolutions at the level of 0.1% for photon energies up to 10 keV and effective source sizes in the range 400–1200 μ m in the dispersive plane. Such wide effective source dimensions are achieved using a double slit system to produce a virtual point-like source between the emitting target and the crystal. The spectrometer performances in terms of reflection efficiency and peak resolution depend on several parameters, among which a special role is played by the crystal mosaicity and thickness. In this work, we report the measurements of the Cu(K α 1 , 2 ) and the Fe(K α 1 , 2 ) lines performed with different mosaicity and thickness crystals in order to investigate the influence of the parameters on the peak resolution and on the reflection efficiency mentioned above.

Bragg spectroscopy of quantum gases: Exploring physics in one dimension

This thesis has been aimed at investigating the dynamical properties of one-dimensional gaseous nanowires, realized by trapping ultracold gases in laser-light lattice structures. The project was carried out at the European laboratory LENS in Florence, also with international collaborations. In recent years, one-dimensional systems have attracted great interest in different fields of physics, material science and chemistry, owing to their peculiar features: In this work, probing the response of the system to inelastic light-scattering experiments – Bragg spectroscopy – has allowed to explore the dynamics and the correlations inside these structures and the quantum phase-transition from superfluid to insulator, occurring due to inter-particle interactions.