The E and B EXperiment (EBEX) is a pointed balloon-borne telescope designed to measure the polarization of the cosmic microwave background (CMB) as well as that from Galactic dust. The instrument is equipped with a 1.5 meter aperture Gregorian-Dragone telescope, providing an 8' beam at three frequency bands centered on 150, 250 and 410 GHz. The telescope is designed to measure or place an upper limit on inflationary B-mode signals and to probe B-modes originating from gravitationnal lensing of the CMB. The higher EBEX frequencies are designed to enable the measurement and removal of polarized Galactic dust foregrounds which currently limit the measurement of inflationary B-modes. Polarimetry is achieved by rotating an achromatic half-wave plate (HWP) on a superconducting magnetic bearing. In January 2013, EBEX completed 11 days of observations in a flight over Antarctica covering 6,000 square degrees of the southern sky. This marks the first time that kilo-pixel TES bolometer arrays have made science observations on a balloon-borne platform. In this thesis we report on the construction, deployment and data analysis of EBEX. We review the development of the pointing sensors and software used for real-time attitude determination and control, including pre-flight testing and calibration. We then report on the 2013 long duration flight (LD2013) and review all the major stages of the analysis pipeline used to transform the ~1 TB of raw data into polarized sky maps. We review "LEAP", the software framework developed to support the analysis pipeline. We discuss in detail the novel program developed to reconstruct the attitude post-flight and estimate the effect of attitude errors on measured B-mode signals. We describe the bolometer time-stream cleaning procedure including removing the HWP-synchronous signal, and we detail the map making procedure. Finally we present a novel method to measure and subtract instrumental polarization, after which we show Galaxy and CMB maps.

The evidence supporting the presence of Dark Matter in the universe ranges over many length scales: from the rotational curves within galaxies that cannot be explained only by the dust and other visible component to the anisotropies in the cosmological microwave background that sets the most precise quantification for the DM content in the universe at 26.8% of the energy density. One of the candidates for DM with the most theoretical support is a family of particles that appear in extensions of the Standard Model of Particles. These new particles, known as Weakly Interacting Massive Particles (WIMPs), provide a natural solution to the missing mass in the universe that interact only via weak interaction and whose origin dates back from the very early universe. The XENON Dark Matter search experiments aim to the direct detection of WIMPs via scattering off xenon nuclei. Following the success of the first prototype, XENON10, the XENON100 detector has been, up to late 2013, the most sensitive DM detector setting an upper bound limit on the spin-independent WIMP-nucleon cross-section of 2. × 10 −45 cm 2 and the spin-dependent equivalent of 3.5 × 10 −44 cm 2 . The detector consists of a dual-phase xenon Time Projection Chamber (TPC) with an inner target of 62 kg, located at the un- derground facility at Laboratori Nazionali del Gran Sasso (LNGS) in Italy. XENON100 is still in operation, currently testing new calibration sources of potential use for the next generation XENON1T experiment, under commissioning in Hall B of LNGS, aims to im- prove the XENON100 sensitivity by two orders of magnitude by increasing the xenon target mass in the detector to the tonne scale and by reducing the intrinsic background rate and consequently, increase the expected number of WIMP events per year. The scale-up of a liquid xenon TPC imposes many technical challenges that needed to be addressed prior to the realization of the XENON1T phase of the project. The focus of my thesis work has been the research and development of Dark Matter detectors operated with a xenon mass at the tonne scale. In particular, the topic of purification of a large amount of Xe gas to reduce the concentration of electronegative impurities to levels below afew parts per billion in a reasonable amount of time has been a driver in my work with the XENON1T Demonstrator facility at the Columbia Nevis laboratories. Two complementary approaches were followed in order to address this problem: i) a study of the performance of XENON100 concerning the electron lifetime (eLT) among other parameters that depend on the purity and ii) the construction of a full-size Xe TPC prototype to test multiple technologies with the goal of an optimized XENON1T TPC, with several tonnes of Xe. In addition to my work on the XENON1T Demonstrator, I have also contributed to the operation and analysis of data from XENON100. In particular, I developed a cut based on the information theory concept of entropy to reduce the electronic noise in the data. A detailed description of the motivation and implementation of the entropy cut is presented in Chapter 3. The experience gained from the successful performance of XENON100 and the information from variety of measurements with the XENON1T Demonstrator have influenced the design of XENON1T and will impact other next-generation Dark Matter detectors using LXe in a TPC. More specifically, the design of the XENON1T cryogenic system which is at the heart of the experiment, has been guided by this experience. The testing of the system was performed at Nevis where the various components were assembled and leak checked before being shipped to LNGS. The XENON1T detector’s cryostat and its cryogenics system, designed by the Columbia University XENON group were installed underground in the Hall B of the LNGS laboratory in Summer/Fall 2014. Their commissioning represent a major milestone in the realization of XENON1T. The last chapter of the thesis summarizes the status of XENON1T, with particular focus on the design of the cryogenic, purification and cryostat system influenced by the R & D with the Demonstrator.