The APEX -SZ instrument: Development, performance and observations

This thesis describes the development, design, instrument performance and observations of the APEX-SZ receiver. APEX-SZ is a millimeter-wave cryogenic receiver designed to observe galaxy clusters via the Sunyaev-Zel'dovich effect from the 12 m APEX telescope on the Atacama plateau in Chile. The receiver consists of a focal plane of 280 superconducting transition edge sensor (TES) bolometers cooled to 280 mK via a three stage He sorption fridge and mechanical pulse tube cooler. The detectors are instrumented with a frequency-domain multiplexed readout system. A horn array, 4 K lenses and tertiary mirrors couple the TES bolometers to the telescope. APEX-SZ observes in a single frequency band at 150 GHz with 59" angular resolution and a 22' field-of-view, well suited for cluster mapping. The receiver represents a leap forward in millimeter wave detector technology. Initial observations with APEX-SZ were early demonstrations of a fielded imaging TES array, frequency multiplexed readout and cryocooled bolometer receiver. These technologies have already been applied to receivers with thousands of detectors.;APEX-SZ typically observes with 180 optically active detectors with an optical efficiency of 0.33 and median NET per channel of 860 μKCMB s . The per channel sensitivity is limited by a bandwidth 40% narrower than expected, and cavity absorption efficiency of 0.74. New detector wafers with wider bandwidth have been fabricated and tested at the telescope on a limited run last spring. With improved bandwidth and lower thermal conductivity, newly fabricated wafers can achieve background noise limited performance. We plan to upgrade the focal plane with a full array of new wafers in December 2009.;The receiver has successfully completed 9 weeks of science observation since its installation in April 2007. We have made over a dozen SZE maps from targeted observations of known clusters. We present SZE temperature maps of the Bullet cluster (1E 0657–56) and Abell 2163.