Search

We describe the development of a detector for precise measurements of the cosmic microwave background polarization. The detector employs a waveguide to couple light between a pair of Mo/Au superconducting transition edge sensors (TES) and a feedhorn. Incorporation of an on-chip ortho-mode transducer (OMT) results in high isolation. The OMT is micromachined and bonded to the microstrip and TES circuits in a low temperature wafer bonding process. The wafer bonding process incorporates a buried superconducting niobium layer with a single crystal silicon layer which serves as the leg isolated TES membrane and as the microstrip dielectric. We describe the micromachining and wafer bonding process and report measurement results of the microwave circuitry operating in the 29–45 GHz band along with Johnson noise measurements of the TES membrane structures and development of Mo/Au TES operating under 100 mK. [ABSTRACT FROM AUTHOR]

We are developing a Transition-Edge Hot-electron Microbolometer (THM) for use in large detector array applications in millimeter-wave astronomy. This bolometer detector consists of a superconducting bilayer TES with an overlapping thin-film semi-metal absorber. The detector is deposited directly on the substrate and thermal isolation of the bolometer is controlled by electron-phonon scattering within the small volume of the detector. We present measurements characterizing the transition behavior of several micron-sized THM test devices which are optimized for photon-noise-limited observations of the Cosmic Microwave Background (CMB). We interpret these measurements in terms of a lateral proximity effect between the TES and the superconducting Nb TES leads. We discuss possible modifications to the THM design to compensate for this effect while retaining the small detector volume necessary to obtain the desired value of electron-phonon thermal conductivity. [ABSTRACT FROM AUTHOR]