International Research Fellowship Program: High Precision Measurement of the Polarization Anisotropy of the Cosmic Microwave Background Radiation

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0402098JohnsonThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-two month research fellowship by Dr. Bradley R. Johnson to work with Dr. Walter Gear at the University of Wales in Cardiff.Recent measurements of the temperature anisotropy of the cosmic microwave background radiation (CMB) from experiments like MAXIMA and WMAP suggest we live in a universe whose evolution is described by adiabatic inflationary cosmology dominated by cold dark matter and a cosmological constant. Given this fact, the CMB should be partially linearly polarized with the vector field on the sky consisting of a curl-free (E-mode) component and a divergence-free (B-mode) component. The E-mode component was predominantly produced by bulk motion in the primordial plasma at recombination arising from scalar perturbations; the B-mode component was produced by tensor perturbations resulting from inflationary gravity waves. A measurement of the angular power spectrum of the primordial B-mode polarization will yield the energy scale of inflation. B. R. Johnson is working as part of the Instrumentation Group at the University of Wales, Cardiff to develop polarimetric instrumentation for making high precision measurements of the polarization of the CMB. This instrument will be specifically designed to characterize the anticipated B-mode signals. The primordial B-mode signal is extremely faint and therefore difficult to detect. Likely instrument designs will employ hundreds of photon noise limited 300 mK bolometric detectors, a ~2 m reflecting telescope large enough to provide ~5 arcmin resolution at 150 GHz, and polarization modulation hardware. Once constructed, integrated and deployed, the experiment will be map ~500 square degree regions of the sky from Antarctica at Dome C where the millimeter-wave emission of the atmosphere is minimized.