The South Pole Telescope (SPT), like its precursor experiment APEX-SZ,makes mm-wavelength observations of the Cosmic Microwave Background (CMB). Both of these experiments utilize large-scale bolometer arrays with Frequency-Domain Multiplexing to read out multiple TES bolometers with one SQUID. Though Frequency-Domain Mutltiplexing was successfully demonstrated well before the deployment of the SPT, there were many system level details that needed to be dealt with when transitioning from a small-scale "proof-of-principle" system to a full kilo-pixel array that has to operate reliably in the field. These changes vary in scope from the thermal design of the bolometers themselves, to the SQUID feedback electronics and the software used to operate these electronics. In this paper we describe some of the systems-engineering details involved in building a multiplexed instrument such as the SPT receiver.
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