The SAFARI Detector System

We give an overview of the baseline detector system for SAFARI, the prime focal-plane instrument on board the proposed space infrared observatory, SPICA. SAFARI's detectors are based on superconducting Transition Edge Sensors (TES) to provide the extreme sensitivity (dark NEP$\le2\times10^{-19}\rm\ W/\sqrt Hz$) needed to take advantage of SPICA's cold (<8 K) telescope. In order to read out the total of ~3500 detectors we use frequency domain multiplexing (FDM) with baseband feedback. In each multiplexing channel, a two-stage SQUID preamplifier reads out 160 detectors. We describe the detector system and discuss some of the considerations that informed its design.Comment: 7 pages, 3 figures, Proc. SPIE 10708, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX, 107080K (9 July 2018); (fixed typo in abstract

Ultrasensitive TES bolometers for space based FIR astronomy

We present results from the development of a background limited transition edge sensor (TES) bolometer for the wavelength band 30–60 μm. The bolometer consists of a Ti∕Au superconducting thermometer and a Ta radiation absorber deposited on a 200μm×300μm membrane of SixNy suspended on long, narrow legs. This device is voltage biased and the current through the device is measured by a SQUID amplifier. The thermometer has transition temperature Tc  =  108 mK and the device is operated from a 70 mK base plate. FIR radiation is coupled into a multimodc horn with entrance aperture of 450 μm, length 4.5 mm and exit aperture of 45 μm, which feeds a metal integrating cavity containing the detector. The radiation band is defined by a pair of lowpass and highpass mesh filters in front of the horn. Here we present measurements of optical noise equivalent power (NEP), optical efficiency, dynamic range and time constant. The results show that measured TES detectors are close to meeting the requirement of the “Band 3” of SAFARI FTS imaging instrument [1] on the SPICA mission [2]