Development of frequency division multiplexing readout for a large transition edge sensor array for space

The light in sub-millimeter and far-Infrared (FIR) wavelengths from deep space can travel in an incredibly long distance and contains rich, unique information, which can help astronomers to reveal the history of the universe and answer outstanding questions such as the origin of galaxies, stars, and planets. Sensitive transition edge sensor (TES) bolometers in combination with frequency division multiplexing (FDM) readout system that can read out multiple pixels simultaneously are the candidate detector technology for several space missions operated at sub-millimeter and FIR wavelengths. My thesis reports the study and development of an FDM-readout system for TES bolometers, containing five main scientific sub-projects focusing on building systematically a readout demonstration system. Characterizing the noise of the readout system is essential. Chapter 3 and 4 report studies of the noise from room- and cryogenic-temperature electrical components, respectively. Chapter 5 presents a map of all pixels in the FDM-system, aiming to reduce the unwanted noise between pixels within a TES bolometer array. Chapter 6 demonstrates an FDM-system that can read out 60 low noise TES bolometers simultaneously. The readout noise of the FDM-system is lower than the noise of highly sensitive detectors and that the sensitivities measured when all pixels in operation are the same as what measured when only one pixel is operated. Chapter 7 shows further improved results on electrical-crosstalk performance and stability of the FDM-system compared to Chapter 6. We report a full demonstration of the FDM-system in the lab, opening the door to the readout for space observatories