UC San Diego

The Cosmic Microwave Background (CMB) is a window into the physics of the early universe, and polarization-sensitive measurements of the CMB allow us to test cosmological theories such as inflation. Achieving the required sensitivity to perform these measurements requires large arrays of highly sensitive cryogenic detectors. This thesis will discuss work on two telescopes.

For LiteBIRD, a satellite scheduled for launch in 2032, the described work addresses the testing and design of the cryogenic readout system. In Chapter 3 a model for readout noise is described and used to estimate readout noise for a range of circuit designs to identify which would meet LiteBIRD’s requirements. In Chapter 4 the effect of modifications to the circuit is tested and the noise model is validated.

For the Simons Array, an array of telescopes currently observing from the Atacama desert, the thesis describes work to optimize the detector performance and model their achieved noise. Chapters 5 and 6 focus on data from POLARBEAR-2b and POLARBEAR-2a respectively, the two telescopes in the Simons Array. In Chapter 5 readout noise in POLARBEAR-2b is found to be consistent with the model applied earlier to LiteBIRD. Early commissioning data of beam sizes, gain and noise are presented. In Chapter 6 a telescope model of POLARBEAR-2a is described and used to estimate detector noise. This is compared to measurements of the detector noise and found to be consistent.