Description
Recent CMB observations aim at detecting the degree-scale B-mode polarization of Cosmic Microwave Background (CMB) whose origin is primordial gravitational waves.
To suppress systematic uncertainties derived from instruments enough for future better observation sensitivity, optical characteristics of CMB telescopes, such as the beam pattern, need careful calibration that evaluates even very minor nonidealities.
In this study, we propose a new calibration measurement method that employs a feedback-controlled power-tunable artificial source, which enables us to measure the optical characteristics in a high dynamic range (e.g. more than 60 dB) and to identify the very minor nonidealities (e.g. 0.0001% level), even if the telescope has detectors that are very easy to saturate such as Transition Edge Sensors (TES).
This poster presentation reports a proof-of-concept demonstration in a laboratory using a common commercial antenna for general use. We achieved a 60 dB dynamic range in its beam pattern measurement in the proposed method, and confirmed that the measured beam pattern agreed with that in common measurement methods.