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The semimetal character of bismuth and its large photon absorbing power make of this element the most suitable absorber material for X-ray low temperature detectors. This application requires coatings of Bi with thicknesses and properties that only electrodeposition methods may achieve. Although there are studies on electrodeposition of bismuth for these detectors and other devices, the process is not straightforward and has not been sufficiently studied in terms of the desired final properties, neither the effect of different parameters is well known or easily reproduced. This work reports the influence of two different electrolytes, of the deposition method, and of heating and stirring on the structure, microstructure and transport properties of bismuth films. Typically, rhombohedral Bi is obtained upon electrodeposition with very good crystallinity, and some crystal preferential orientation, while significant empirical correlations are found among electrochemical parameters, microstructure, and resistivity. Such correlation allows the identification of the deposition parameters for coatings that yield the optimal functional properties.

Microwave Kinetic Inductance Detectors (MKIDs) are a superconducting detector technology capable of measuring photon arrival times to the microsecond level with moderate energy resolution. MKIDs are essentially superconducting microresonators, and when a photon is incident on the inductor portion of the microresonator, the inductance temporarily increases and the resonant frequency decreases. An array of MKIDs can be naturally multiplexed and read out by assigning each detector a unique resonant frequency during fabrication and coupling the detectors to a single transmission line. A frequency domain multiplexing scheme can then be used to pass a microwave frequency comb through the transmission line to probe the microresonators and listen for photon events. In order to meet the demands of the next generation of astronomical instrumentation, MKIDs need improvements in three main areas: pixel yield, energy resolution, and quantum efficiency. I have investigated new fabrication techniques and materials systems to address these issues. Most notably, I have fabricated MKIDs with platinum silicide as the superconducting layer and have measured especially high resonator internal quality factors (>10^6). Platinum silicide films can also be made much more uniformly than the traditional sub-stoichiometric titanium nitride films used in the field, increasing pixel yield. In addition, platinum silicide intrinsically has a higher absorption rate for optical photons than titanium nitride. These platinum silicide detectors are used in two new MKID planet imaging instruments, the Dark-speckle Near-IR Energy-resolved Superconducting Spectrophotometer (DARKNESS) and the MKID Exoplanet Camera (MEC). Optical MKIDs have already been demonstrated on sky with the first generation MKID instrument, the Array Camera for Optical to Near-IR Spectrophotometry (ARCONS). I have used ARCONS to primarily observe compact objects, such as AM CVn systems and detached white dwarfs. In particular, I

Microwave Kinetic Inductance Detectors (MKIDs) are a superconducting detector technology capable of measuring photon arrival times to the microsecond level with moderate energy resolution. MKIDs are essentially superconducting microresonators, and when a photon is incident on the inductor portion of the microresonator, the inductance temporarily increases and the resonant frequency decreases. An array of MKIDs can be naturally multiplexed and read out by assigning each detector a unique resonant frequency during fabrication and coupling the detectors to a single transmission line. A frequency domain multiplexing scheme can then be used to pass a microwave frequency comb through the transmission line to probe the microresonators and listen for photon events. In order to meet the demands of the next generation of astronomical instrumentation, MKIDs need improvements in three main areas: pixel yield, energy resolution, and quantum efficiency. I have investigated new fabrication techniques and materials systems to address these issues. Most notably, I have fabricated MKIDs with platinum silicide as the superconducting layer and have measured especially high resonator internal quality factors (>10^6). Platinum silicide films can also be made much more uniformly than the traditional sub-stoichiometric titanium nitride films used in the field, increasing pixel yield. In addition, platinum silicide intrinsically has a higher absorption rate for optical photons than titanium nitride. These platinum silicide detectors are used in two new MKID planet imaging instruments, the Dark-speckle Near-IR Energy-resolved Superconducting Spectrophotometer (DARKNESS) and the MKID Exoplanet Camera (MEC). Optical MKIDs have already been demonstrated on sky with the first generation MKID instrument, the Array Camera for Optical to Near-IR Spectrophotometry (ARCONS). I have used ARCONS to primarily observe compact objects, such as AM CVn systems and detached white dwarfs. In particular, I

The oscillation experiments have clearly shown that neutrino are massive particle. Nowadays the experiments based on kinematic analysis of electrons emitted in nuclear beta-decay are the most sensitive for a direct electron-neutrino mass determination. The method consists in searching for a tiny deformation caused by a non-zero neutrino mass to the spectrum of the charged particles emitted near the end point. A possible approach is the calorimetric one. In a calorimetric measurement the source is embedded in the detector and all the energy is measured, except for the one taken away by the neutrino. A drawback of this approach is that the full spectrum is acquired, while only the decays very close to the end-point are useful for measuring the neutrino mass. Therefore, the source activity has to be limited to avoid pile-up which would deform the shape of beta spectrum. As a consequence the statistics near the end-point is limited as well. This limitation may be then partially balanced by using isotopes with an end-point energy as low as possible. In this scenario an international collaboration has grown around the project of Microcalorimeter Arrays for a Rhenium Experiment (MARE) for a direct calorimetric measurement of the neutrino mass with sub-electronvolt sensitivity. Although the baseline of the MARE project consists in a large array of rhenium based thermal detectors, a different option for the isotope is also being considered. The two competing isotopes are 187Re and 163Ho. While the first beta decays, the latter decays via electron capture, and both have a Q value around 2.5 keV. The MARE project has a staged approach. The first phase of the project (MARE-1) is a collection of activities with the aim of sorting out both the best isotope and the most suited detector technology to be used for the final experiment. The goal of the last phase (MARE-2) is to achieve a sub-eV sensitivity on the neutrino mass. It will deploy several arrays of thermal microcalorimeter, 1714, open, open, Ferri, Ferri, E