Mr. Thomas Alford Profile

Thomas Alford

at Univ of Chicago

SPIE Involvement:

Author

Publications (9)

Proceedings Article | 11 September 2024 Poster + Paper

The Simons Observatory: laboratory beam characterization for the first small aperture telescope

Remington Gerras, Thomas Alford, Michael Randall, Joseph Seibert, Grace Chesmore, Kevin Crowley, Nicholas Galitzki, Jon Gudmundsson, Kathleen Harrington, Bradley Johnson, J. Lloyd, Amber Miller, Max Silva-Feaver

Proceedings Volume 13094, 130945M (2024) https://doi.org/10.1117/12.3019416

KEYWORDS: Optical simulations, Holography, Near field, Telescopes, Sensors, Near field optics, Optical testing, Signal detection, Beam analyzers, Staring arrays

Read Abstract +

The Simons Observatory is a ground-based telescope array located at an elevation of 5200 meters, in the Atacama Desert in Chile, designed to measure the temperature and polarization of the cosmic microwave background. It comprises four telescopes: three 0.42-meter small aperture telescopes (SATs), focused on searching for primordial gravitational waves, and one 6-meter large aperture telescope, focused on studying small-scale perturbations. Each of the SATs will field over 12,000 TES bolometers, with two SATs sensitive to both 90 and 150GHz frequency bands (SAT-MF1, and SAT-MF2), while the third SAT is sensitive to 220 and 280GHz frequency bands. Prior to its deployment in 2023, the optical properties of SAT-MF1 were characterized in the laboratory. We report here on measurements of beam maps acquired using a thermal source on SAT-MF1, along with measurements of near-field beam maps using a holographic method that enables characterization of both the amplitude and phase of the beam response, yielding an estimate of the far-field radiation pattern received by the telescope. We find that the near-field half-width-half-maximum (HWHM) requirements are met across the focal plane array for the 90GHz frequency band, and through most of the focal plane array for the 150GHz frequency band. Namely, the mean of the bandpass averaged HWHM of the edge-detector universal focal plane modules match the simulated HWHM to 10.4%, with the discrepancy caused by fringing in the simulation. The measured radial profile of the beams matches simulations to within 2dB from the beam center to at least the -10dB level. Holography estimates of the far-field 90GHz beams match the full-width-half-maximum from simulation within 1%, and the beam radial profiles deviate by less than 2dB inside the central lobe. The success of the holography and thermal beam map experiments confirmed the optical performance were sufficient to meet the science requirements. SAT-MF1 was deployed to Chile in June, 2023. On-site observations are currently underway.

Proceedings Article | 17 August 2024 Poster

Development and testing of the frequency-selectable laser source (FLS) for Simons Observatory bandpass calibration

Shreya Sutariya, Kathleen Harrington, Carlos Sierra, Erin Healy, Sara Simon, Thomas Alford, Claire Lessler, Jeff McMahon

Proceedings Volume PC13102, PC1310223 (2024) https://doi.org/10.1117/12.3021145

Proceedings Article | 17 August 2024 Poster

The Simons Observatory: in-lab optical testing and validation for the first small aperture telescope

Michael Randall, Thomas Alford, Remington Gerras, JB Lloyd, Joseph Seibert, Kevin Crowley, Shannon Duff, Nicholas Galitzki, Kathleen Harrington, Johannes Hubmayr, Bradley Johnson, Brian Keating, Max Silva-Feaver, Yuhan Wang, Kaiwen Zheng

Proceedings Volume PC13102, PC131021E (2024) https://doi.org/10.1117/12.3020265