The South Pole Telescope SZ-Receiver Detectors

We will discuss the design, fabrication, and testing of a 960-element TES array installed on the new 10 meter South Pole Telescope (SPT). This array is designed to survey for galaxy clusters using the Sunyaev-Zel'dovich (SZ) effect, which is the inverse-Compton scattering of Cosmic Microwave Background photons by plasma bound to clusters of galaxies. The SPT bolometer array consists of fully lithographed spider-web absorbers fabricated on adhesive-bonded silicon wafers with an embedded metal back plane. The absorbers are connected to aluminum-titanium bilayer TESs with a transition temperature of approximately 550 mK. Additional normal-metal features adjust the devices' thermal properties to suit our readout system and observational strategy. The focal plane is cooled using a commercial, closed cycle, pulse-tube refrigerator and a three-stage helium sorption refrigerator with a 250 mK base temperature.