PolarBeaR: Polarization of Background Radiation

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Polarbear has been designed to measure extremely small fluctuations in polarization. Although the Antenna-Coupled TES's are naturally sensitive to polarization, an instrument capable of measure tiny signals in the presence of large varying signals will do much better if the signal is modulated and synchronously detected. Physicists have long used such techniques with a lockin amplifier. Polarbear employs a rotating Half-Wave-Plate to modulate the incoming polarization. The signal is then demodulated using the recorded HWP position. This technique provides immunity to a number of instrumental systematic effects, such as 1/f noise or scan-synchronous noise.