James Cornelison, Ph.D.

Maria Goeppert-Mayer Postdoctoral Fellow at Argonne National Laboratory
Associate Fellow in the Department of Astronomy and Astrophysics at the University of Chicago

I develop and build millimeter-wave telescopes that observe the cosmic microwave background (CMB), as well as the tools used to characterize their performance. My recent interests have drawn me towards developing the cameras used on those telescopes in order to push the limits on the sensitivity of next-generation cosmological experiments.

CMB Polarization Experiments

Cosmic Inflation is a yet-unproven supplemental theory to the Standard Model, supplying elegant solutions to unexplainable observations in the universe. Cosmic inflation also predicts a unique polarization signal in the cosmic microwave background (CMB). I collaborate with BICEP/Keck and the South Pole Telescope to build experiments that are sensitive to tiny differences in CMB polarization to search for this unique signal, which would serve as a robust confirmation of the theory.

Characterization and Systematics

As the search for inflationary signals continues, CMB telescopes are becoming more and more sensitive. As a result, our data becomes increasingly impacted by minor imperfections in the telescopes' construction. To that end, I build customized millimeter-wave instruments to characterize certain aspects of our telescopes' performance. I then use those performance data to understand how deviations between telescopes' design and reality impact the statistical and systematic uncertainty on our constraints on inflation.

Cosmic Birefringence

Telescope characterization has benefits beyond understanding the systematic impact on inflation measurements. I use polarization calibration data in combination with CMB data to search for signals of Cosmic Birefrginence -- the rotation of linearly polarized light as it propagates through the universe. The discovery of Cosmic Birefringence would be serve a the first-ever evidence of parity violation in the electromagnetic force.

Microwave Kinetic Inductance Detectors

A microwave kinetic inductor detector (MKID) is a superconducting camera technology under development as a viable replacement of the transition edge sensor (TES). MKID research is driven by their potential to simplify device layouts, reduce cryogenic load, and increase multiplexing capability. My research at Argonne National Laboratory is in creating new fabrication processes and materials to improve noise perfomance, pixel packing density, and spectral resolution of MKID-based cameras.

Publications

BICEP/Keck XVIII: Measurement of BICEP3 polarization angles and consequences for constraining cosmic birefringence and inflation
Phys. Rev. D (Accepted) | arXiv:2410.12089

Improved Polarization Calibration of the BICEP3 CMB Polarimeter at the South Pole
SPIE | arXiv:2207.14796

BICEP / Keck XV: The BICEP3 CMB Polarimeter and the First Three Year Data Set
Astrophysical Journal | arXiv:2110.00482

BK-XIII: Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018 Observing Season
Phys. Rev. Lett. | arXiv:2110.00483

Contact Information