Design, realization, and characteristics of a transition edge bolometer for sub-millimeter wave astronomy

The large array bolometer camera is scheduled to succeed its semiconducting predecessor at the Atacama pathfinder experiment. It shall be an array of 300 transition edge sensors operated at a temperature of about 0.25 K, provided by a (3)He evaporation cooler and a pulse tube refrigerator. The instrument will be read out by a superconducting quantum interference device time domain multiplexer. The design and realization of a suitable detector for this instrument is described. Based on sensitivity demands derived from the background limit, the thermal and electrical designs for a spider-web bolometer are deduced. The theoretical predictions are compared to experimental results. The pixel design yields a background-limited performance for background loads corresponding to blackbody sources between 77 K and 300 K and a partially effective anti-aliasing filter for the intended multiplexed readout.