Ultra-sensitive transition-edge sensors for the Background Limited Infrared/Sub-mm Spectrograph (BLISS)

Abstract

We report progress in fabricating ultra-sensitive superconducting transition-edge sensors (TESs) for BLISS. BLISS is a suite of grating spectrometers covering 35-433μm with R~700 cooled to 50mK that is proposed to fly on the Japanese space telescope SPICA. The detector arrays for BLISS are TES bolometers readout with a time domain SQUID multiplexer. The required noise equivalent power (NEP) for BLISS is NEP=10-19 W/Hz1/2 with an ultimate goal of NEP= 5 × 10-20 W/Hz1/2 to achieve background limited noise performance. The required and goal response times are τ=150ms and τ=50ms respectively to achieve the NEP at the required and goal optical chop frequency 1-5Hz. We measured prototype BLISS arrays and have achieved NEP=6 × 10-18 W/Hz1/2 and τ=1.4ms with a Ti TES (TC=565mK) and NEP~2.5 × 10-19 W/Hz1/2 and τ~4.5ms with an Ir TES (TC=130mK). Dark power for these tests is estimated at 1-5fW.PACS numbers: 85.25.Pb; 95.85.Gn; 95.85.Fm; 63.22.+m