Stephen Padin: Research

My research is in instrumentation for astronomy. I am interested in interferometry, optical and radio telescope design, and observations of the cosmic microwave background radiation.

Detectors

I worked on superconducting transition edge sensors for a new, 16,000-pixel, millimeter-wavelength camera for the South Pole Telescope. The camera will measure polarization of the cosmic microwave background radiation. My main contribution to the detectors was the development of gold-titanium-gold films that have sharp, repeatable, normal to superconducting transitions.

3gDetectorArray]

Submilimeter-wavelength Astronomy

I was the Chief Engineer for CCAT, a 25-m submillimeter-wavelength telescope to be located on Cerro Chajnantor in the Atacama Desert. CCAT is designed to measure the rate of star formation over cosmic time, which is key to understanding how galaxies are assembled. My main contribution to CCAT was the wide-field optical design, with many sub-field cameras combined to achieve unprecedented mapping speed, and the use of carbon fiber reinforced plastic for the mirror support structures.

CCAT]

The Cosmic Microwave Background Radiation

I was the Project Manager for the South Pole Telescope (SPT), a 10-m off-axis Gregorian telescope equipped with a wide-field millimeter-wavelength bolometer camera. The SPT is surveying galaxy clusters using the Sunyaev-Zel'dovich effect, and measuring polarization of the cosmic microwave background radiation. It is located at the Amundsen-Scott South Pole Station in Antarctica. My main contribution to the SPT was the optical design, which is a classical Gregorian with a cold stop surrounding the secondary.

SPT]

I was the Project Scientist for the Cosmic Background Imager (CBI), an interferometer array which measured the angular power spectrum of fluctuations in the 3K cosmic microwave background radiation. Our results confirmed the presence of a damping tail and high-order Doppler peaks, which are key predictions of the standard Big Bang models. The CBI had thirteen 1-m antennas, with cooled receivers operating at a wavelength of 1 cm. It was located in the Atacama Desert at an altitude of 5000 m. My main contribution to the CBI was a 10-GHz bandwidth analog correlator.

CBI]

Optics

I developed performance and cost models for the California Extremely Large Telescope, a 30-m optical telescope with a segmented primary mirror. The emphasis of this work was on modeling wind buffeting, vibrations, and mirror control.

Millimeter-wave Interferometry

I designed local oscillators, analog & digital correlators, and wideband SIS receivers for the Owens Valley Millimeter Array. This is an Earth rotation synthesis array comprising six 10-m antennas, with receivers operating in the 3-mm and 1-mm bands. The array is now part of CARMA and supports research in many fields, including star formation, protoplanetary systems, galactic structure, active galaxies, and cosmology. My main contribution to the instrument was a high-speed digital correlator and wideband SIS mixers with integrated HEMT IF amplifiers.

OVRO Millimeter Array]


Publications, Professional Experience

Stephen Padin spadin@uchicago.edu
2017 May 20