MRI-R2: Development of POLAR-1, an expandable 5,000-detector CMB Polarimeter

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The Cosmic Microwave Background (CMB) observations hold a remarkable wealth of information about the early Universe and they recently transformed cosmology into a precision science. While the basic notion and the ingredients of an expanding Universe are well established, fundamental questions on the Universe's origin still remain unanswered. Measuring the CMB polarization provides a powerful tool to address the most important of these questions. The polarization pattern in the CMB can be decomposed into two distinct components, E-mode and B-mode, and the latter (yet to be detected) can provide two remarkable insights. With the detected B-mode polarization, one can study the large-scale structure of the Universe and the parameters that affect this structure, such as absolute neutrino mass and Dark Energy evolution. The degree-scale B-mode polarization also should carry imprints from the Cosmic Gravitational-wave Background (CGB), giving us a glimpse of the Universe during its tiniest (10^-35) fraction of the very first second of life. This CGB signal is a direct measurement of the energy scale at which the inflationary Big Bang occurs. The proposal requests funds for development of an enhanced large-format focal plane polarimeter POLAR-1 with 4,608 polarization-sensitive superconducting bolometers operating at 150 GHz and integrated with a 1.5-m reflective radio telescope. The proposed combination of angular resolution and bolometer array size make it ideally suited to study both the lensing-induced and the CGB-generated B-polarization. POLAR-1 will detect lensing induced B-polarization with extremely high significance and search for CGB down to 2% of the initial perturbation in power. The project's broader impacts would be in its path-finding nature of building an instrument ~10x more sensitive to the CMB polarization. As cosmology captures the public imagination, it is a remarkably effective vehicle for stimulating students' interest in science. The project will continue contributing significantly to the training of next generation of scientists by integrating graduate and undergraduate education with technology and instrumentation development, astronomical field observations, and scientific analysis.