Development of new generation receivers for experimental cosmology with the cosmic microwave background and systematic effect studies

Thesis

Most of current and future Cosmic Microwave Background (CMB) Radiation experiments are targeting the polarized B-mode signal. The small amplitude of this signal makes a successful measurement challenging for current technologies. Therefore, very accurate studies to mitigate and control possible systematic effects are vital to achieve a successful observation. An additional challenge is coming from the presence of polarized Galactic foreground signals that contaminate the cosmological signal. When they are combined, the foreground signals dominate the polarized CMB signal at almost every relevant frequency. Future experiments, like the LiteBIRD space-borne mission, aim at measuring the CMB B-mode signal with high accuracy to measure the tensor-to-scalar ratio r at the 10⁻³ level.

In this thesis, after briefly introducing the science case, the LiteBIRD mission and some of its key technologies, we focus on a few systematic effects concerning mostly the band-pass response. In this context we present novel studies to determine the impact of band-pass uncertainties on the data.

Good control over the response of the superconductive detector is another key ingredient for the success of the mission. We present our modelling of the detector response and a framework to study non-linearity effects due to thermal and optical loading fluctuations.

Lastly, we present results of detector characterization using a test-bed under development that will be used to further our understanding of the interaction between various telescope sub-systems.

Authors: Ghigna, T

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English