Development of Space-Optimized TES Bolometer Arrays for LiteBIRD

LiteBIRD is a cosmic microwave background polarization experiment with the goal of measuring the tensor-to-scalar ratio with a total uncertainty of $$\delta r <0.001$$ δ r < 0.001 . It will survey the full sky from space for 3 years in 15 frequency bands spanning 34–448 GHz. We are developing detector arrays for the six lowest frequency bands covering 34–99 GHz. The arrays are populated with lenslet-coupled sinuous antennas, triplexer bandpass filters, and transition-edge sensor (TES) bolometers. We have measured the electrical and thermal properties of several TES designs to determine space-optimized parameters. The design balances requirements for low saturation power of the space environment while maintaining a fast time response for use with a continuously rotating half-wave plate. We have achieved detector saturation powers below 1 pW, with time constants faster than 1 ms, at a 100 mK bath temperature measured using both time- and frequency-division multiplexed SQUID readout systems. Using this information, we have fabricated multi-chroic pixels with antenna-coupled space-optimized bolometers.