LiteBIRD Low- and mid-frequency detectors: design and status

Abstract

The Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection (LiteBIRD) is a space mission to search for and characterize the signature of inflation in the polarized signal from the cosmic microwave background (CMB), and probe fundamental physics. LiteBIRD will precisely measure the polarization of the cosmic microwave background on large angular scales ≳ 1 deg. It will survey the full sky with three telescopes covering 15 frequency bands centered at frequencies from 40 to 402 GHz. The pixel design for the low- and mid-frequency telescopes features a hemispherical lenslet coupled to a broadband sinuous antenna. The radiation detected by the sinuous antenna propagates through a superconducting microstrip and on-chip bandpass filters before being detected by superconducting transition edge sensor (TES) bolometers. The TES design fulfills 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 present measurements of the electrical and thermal properties of the TES detectors with values required for the LiteBIRD mission, the design and measurements of a dual-polarization trichroic pixel at 40, 60, and 78 GHz suitable for the low-frequency telescope, and the design and preliminary measurements for a detector array at 100, 140, and 195 GHz suitable for the mid-frequency telescope.