Astrophysics Seminar

Measurements of the cosmic microwave background (CMB) have provided the most precise picture of the early Universe and validated the ΛCDM model of cosmology. Measurement of CMB polarization anisotropies on the largest angular scales is a powerful way to constrain the optical depth to reionization and search for the signature of primordial gravitational waves from inflation. The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that has been observing nearly 75% of the sky from the Atacama Desert in Chile at frequency bands centered near 40, 90, 150, and 220 GHz. I will talk about how the CLASS instrument and survey strategy enable recovery of the largest angular scale CMB polarization signal from the ground. I will discuss results from the CLASS 40 GHz channel. I will also describe the design of the latest 90 GHz CLASS detectors and talk about optical characterization of the telescopes.