ANALYSIS OF THE STRIP OPTICAL SYSTEM FOR CMB POLARIZATION MEASUREMENTS

Nowadays, the detection of B-mode polarization anisotropies on large angular scales in the Cosmic Microwave Background polarization pattern is one of the major challenges in observational cosmology. In fact, it would give us an evidence in favor of the inflationary paradigm, shedding light on the physics of the very early Universe. Unfortunately, the amplitude of the signal is extremely low, at fractions of µK, and its detection requires high sensitivity instruments with thousands of detectors, a rigorous control of systematic effects, and a precise knowledge of the foreground polarized emission of our Galaxy. The Large Scale Polarization Explorer is one of the upcoming experiments devoted to the observation of the CMB polarization on large angular scales. It is based on two independent instruments: the STRIP ground-based telescope and the SWIPE balloon-borne mission. This thesis has been carried out in the context of the development of the STRIP instrument, a coherent polarimeter array that will observe the microwave sky from the Teide Observatory in Tenerife in two frequency bands centred at 43 and 95 GHz through a dual-reflector crossed-Dragone telescope of 1.5 m aperture. We present the implementation of the realistic electromagnetic model of the STRIP telescope, which includes all its optical elements and the surrounding structures. Since accurate predictions and measurements of the beam shape are essential both during the instrument design phase and for an in-depth knowledge of the whole-instrument response, we performed detailed optical simulations of the beam radiation properties. The results have been essential to assess the impact of the optical response on CMB polarization measurements when observing the sky with the nominal scanning strategy. This activity was mandatory because the optics is one of the major limiting factors for high precision measurements.