Ultra-low noise TES bolometer arrays for the US SAFARI contribution

Abstract

We are developing ultra-low noise transition edge sensor (TES) bolometer arrays for the long-wavelength grating spectrometer modules of SAFARI, part of the cryogenically-cooled SPICA mission now in phase-A study in Europe.  These devices target a per-pixel noise equivalent power (NEP) below 10^-19 WHz^-1/2 with a time-constant faster than 10ms.  The SAFARI focal planes will be cooled to 50 mK, and we use a 100 mK thermistor formed from an annealed Titanium-Gold bilayer film.  To minimize excess heat capacity, we have developed a new wet-release process which provides high yield in large (~250-pixel) sub-arrays.  We will report on the fabrication, testing, and achieved performance of these detectors. We will also present the focal plane assembly designed to support the 5 (spatial) x 180 (spectral) format coupled to spectrometers thru multimodes horns.  The focal plane is composed of four monolithic sub-arrays with integrated backshorts, all integrated onto a large silicon substrate.