MRI: Development of a Sensitive Broadband Dual-Frequency Millimeter-Wavelength Polarimeter

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The development of a unique sensitive broadband dual-frequency millimeter-wavelength polarimeter is proposed by C. Bennett (Johns Hopkins University) for the primary purpose of detecting gravitational waves from the first moments of the universe. The polarimeter will be used to answer fundamental questions such as, "How did the universe begin?" In cosmology, Inflation is the cornerstone of the standard model, and the polarimeter data will provide a greatly improved limit or discovery of the energy level of Inflation. In physics, detection of a specific polarization pattern would be a detection of gravitational waves. These tests will be made using signals from the cosmic microwave background (CMB), over the full range of angular scales on which the primordial gravitational radiation leaves its strongest imprint.The proposed polarimeter uses dichroic detectors to operate simultaneously at 130-165 GHz and 200-234 GHz. These bands both provide extra sensitivity for the Cosmology Large Angular Scale Surveyor (CLASS) array to the polarized CMB and serve as a sensitive probe to identify and isolate polarized Galactic dust emission. When combined with the lower frequency CLASS instruments, the scientific impact of the original hardware investment is greatly amplified. The capability of CLASS is accentuated by its sensitivity to angular scales 10 degrees. From its Atacama site in northern Chile, not far from the equator, CLASS will survey 70% of the sky, overlapping the sky areas surveyed by the other northern and southern hemisphere observatories, and enabling the kind of multi-band data from multiple observatories that has proved so useful in the past. As all CLASS data will be made public, they will be of legacy value to the entire community.Funding for the development of the dual-frequency polarimeter for the study of inflation and gravitational waves in the early universe is being provided by NSF's Division of Astronomical Sciences through its participation in the Major Research Instrumentation program.