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Title: Detector technology for CMBR applications and for the high frequency detection of polarised foregrounds
Author: Dunlop, L.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2008
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The technology described here lends itself particularly well to the detection of the B-mode polarisation signal intrinsic to the Cosmic Microwave Background Radiation (CMBR). It is unclear as to whether the B-mode polarisation detection limit will be due to detector sensitivity or due to foreground contamination. Part 1 focuses on fabricating the best possible devices, where sensitivity approaches the phonon noise limit, whereas in Part 2 I predict a limit presented by extragalactic foreground radio sources at frequencies approaching the CMBR observing frequency. The planar technology presented in Part 1 consists of a microstrip-coupled transition edge sensor (TES) that uses a finline taper to transfer between waveguide and superconducting Nb microstrip. The microstrip transports the signal to a matched Au/Cu resistor, which is deposited on a thermally isolated SiN membrane. The dissipated RF power causes the resistance of a Mo/Cu TES bilayer to increase, and the resulting reduction in bias current is read out by a SQUID. This technology may be combined with waveguide-horn technology to produce sensitive bolometric detectors with well-defined, single-mode beam patterns and polarisation characteristics. Finally, in Part 2 I concentrate on 43 sources from the 9C follow up survey. The data is used to provide insight into the population of radio foreground sources at 5 and 22 GHz in Stokes parameters I, Q and U. These values are then used to predict the Angular Power Spectrum (APS) contribution of the sample, which are compared to the APS of the B-mode polarisation signal that is intrinsic to the CMBR. This part of the Thesis contributes to the small amount of published work on the feasibility of detecting the B-mode polarisation signal of the CMBR by considering the foreground contribution of extragalactic radio sources.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available