J Choi
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3 records found
1
GroundBIRD
A CMB Polarization Experiment with MKID Arrays
GroundBIRD is a ground-based experiment for a precise observation of the cosmic microwave background (CMB) polarizations. To achieve high sensitivity at large angular scales, we adopt three features in this experiment: fast rotation scanning, microwave kinetic inductance detector (MKID), and cold optics. The rotation scanning strategy has the advantage to suppress 1/f noise. It also provides a large sky coverage of 40%, which corresponds to the large angular scales of l∼ 6. This allows us to constrain the tensor-to-scalar ratio by using low l B-mode spectrum. The focal plane consists of 7 MKID arrays for two target frequencies, 145 GHz and 220 GHz band. There are 161 pixels in total, of which 138 are for 145 GHz and 23 are for 220 GHz. This array is currently under development, and the prototype will soon be evaluated in telescope. The GroundBIRD telescope will observe the CMB at the Teide observatory. The telescope was moved from Japan to Tenerife and is now under test. We present the status and plan of the GroundBIRD experiment.
Engineering faces many wicked problems: irreducibly interdisciplinary with multiple competing objectives, and of such large scale and complexity that will require processes to deeply rely on human insights and power of computation. The resurgence of machine learning offers the possibility for new forms of human/computer collaboration where each fuels hybrid intelligence in complementary ways. A concept of virtual design assistant (VDA) is developed as a platform to bring the hybrid intelligence in solving complex design challenges. A deep learning-based abstraction process is developed to provide VDA a function to extract structured functional requirements from fragmental design specifications and customer needs.
GroundBIRD
Observation of CMB Polarization with a Rapid Scanning and MKIDs
Cosmic microwave background (CMB) radiation is an afterglow from the Big Bang. CMB contains rich information about the early stage of the universe. In particular, odd-parity patterns (B-mode) in the CMB polarization on a large angular scale would provide an evidence of the cosmic inflation. The aim of the GroundBIRD experiment is to observe the B-mode on large angular scales from the ground. One of the most novel characteristics of the telescope used for this experiment is its rapid rotational scanning technique. In addition, the telescope uses cold optics and microwave kinetic inductance detectors. We have developed a telescope mount with a three-axis rotation mechanism (azimuth, elevation, and boresight) and measured the vibration at the focal plane stage at 20 RPM scan rotation rate. We also performed focal plane detector tests on this mount. The tests confirmed the expected response from the geomagnetism associated with the mount rotation. We have also developed a design for the magnetic shields and a detector array on a 3-in wafer. The preparations to begin the observations at the Teide Observatory in the Canary Islands in 2018 are proceeding smoothly.