Measuring the Cosmic Microwave Background Radiation from Chile

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Precise measurement of the cosmic microwave background (CMB) radiation holds the key to a surprising quantity of knowledge about cosmology and the early universe. Measurement of the power spectrum of the CMB yields information about inflation and gravitational waves in the early universe, the mass of the neutrino, and the number of effective neutrino species. As CMB photons pass through our universe, the interaction they have with its contents yield even more information. Scattering of the CMB photons off of the electrons in galaxy clusters can be used to extract the movement of those galaxy clusters, and gravitational lensing of the CMB photons tells the story of the evolution of massive structures in our universe. Extracting this information requires an extreme level of precision and care in the detection of these photons. This dissertation covers a number of subjects related to measuring CMB photons with telescopes in Chile. I first discuss the superconducting transition edge sensors used on some of these telescopes, and the testing and characterization of these sensors for the Simons Observatory. It is necessary to multiplex the detector signals to reduce thermal load on the cryostat cold stages, so I then discuss testing and characterization strategies for superconducting multiplexers. This begins with characterization of the time domain multiplexing chips used on Advanced ACTPol, and leads into characterization of microwave multiplexing chips like those that will be used in the Simons Observatory. Next, I present methods for designing and optimizing wide area CMB survey strategies from Chile, including the strategies that are used in Advanced ACTPol and the strategies that will be used in the Simons Observatory. I then describe recent results from the Atacama Cosmology Telescope that this work has contributed to. I conclude by summarizing the improvements we will see in measurements of the CMB from new observatories in the coming years.

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167 pages


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Cosmic Microwave Background; Cosmology; Multiplexing; Observing Strategy; Survey Strategy; Transition Edge Sensors


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Union Local


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Committee Chair

Niemack, Michael D.

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Bean, Rachel E.
Nowack, Katja C.

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Ph. D., Physics

Degree Level

Doctor of Philosophy

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Government Document




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Attribution-NonCommercial 4.0 International


dissertation or thesis

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