Seminarios de Instrumentación
GroundBIRD — Observation of CMB polarization with wide-sky survey and fast rotation scanning

Abstract

GroundBIRD is a millimeter-wave telescope to observe the polarization patterns of the cosmic microwave background (CMB). The telescope scans at a high rotation speed (20 revolutions per minute), and observes ~40% full sky with suppressed atmospheric 1/f noise. High-sensitivity detector arrays of MKIDs (microwave kinetic inductance detectors) are utilized to obtain the fast time response of >1kHz. The cryogenic system keeps the detectors at 250mK for over 24 hours with 20rpm rotation. The data acquisition system is implemented using field-programmable gate arrays (FPGAs), which realizes flexibly changing frequencies, multiplexing, powers, and also sampling rate for each MKID array. Communication between the detector and other angular readout systems was also established for timing synchronization where the sub-millisecond resolution with 120°/sec rotation is required. The telescope was developed in Japan, and installed at Teide Observatory in September 2019. We have demonstrated that all systems are working correctly by observing the moon.