Millimeter-wave bolometer array receiver for the Atacama pathfinder experiment Sunyaev-Zel'dovich (APEX-SZ) instrument

摘要

The Atacama pathfinder experiment Sunyaev-Zel'dovich (APEX-SZ) instrument isa millimeter-wave cryogenic receiver designed to observe galaxy clusters viathe Sunyaev-Zel'dovich effect from the 12 m APEX telescope on the Atacamaplateau in Chile. The receiver contains a focal plane of 280 superconductingtransition-edge sensor (TES) bolometers instrumented with a frequency-domainmultiplexed readout system. The bolometers are cooled to 280 mK via athree-stage helium sorption refrigerator and a mechanical pulse-tube cooler.Three warm mirrors, two 4 K lenses, and a horn array couple the TES bolometersto the telescope. APEX-SZ observes in a single frequency band at 150 GHz with1' angular resolution and a 22' field-of-view, all well suited for clustermapping. The APEX-SZ receiver has played a key role in the introduction ofseveral new technologies including TES bolometers, the frequency-domainmultiplexed readout, and the use of a pulse-tube cooler with bolometers. As aresult of these new technologies, the instrument has a higher instantaneoussensitivity and covers a larger field-of-view than earlier generations ofSunyaev-Zel'dovich instruments. The TES bolometers have a median sensitivity of890 uKcmb-sqrt(s) (NEy of 3.5e-4 sqrt(s)). We have also demonstrated upgradeddetectors with improved sensitivity of 530 uKcmb-sqrt(s) (NEy of 2.2e-4sqrt(s)). Since its commissioning in April 2007, APEX-SZ has been used to map48 clusters. We describe the design of the receiver and its performance wheninstalled on the APEX telescope.