Calibration system with cryogenically-cooled loads for cosmic microwave background polarization detectors

Area of Science:

• Astrophysics
• Cosmology
• Instrumentation

Background:

• Accurate calibration of polarimeters is crucial for cosmic microwave background (CMB) polarization measurements.
• Existing calibration methods may not fully replicate the faint polarized signals observed in space.

Purpose of the Study:

• To introduce a novel laboratory system for calibrating millimeter-wave polarimeters.
• To enable the simulation of faint polarized signals (∼100 mK) in a controlled environment.

Main Methods:

• The system extends conventional metal mirror rotation techniques.
• It utilizes cryogenically-cooled blackbody absorbers to generate a slightly polarized signal.
• The design and principle of the calibration system are detailed.

Main Results:

• The system successfully generates a polarized signal at a level comparable to ground-based CMB observations.
• Demonstrated the system's utility with a coherent-type polarimeter for CMB experiments.
• The technique is applicable to both coherent and incoherent polarimeters.

Conclusions:

• This novel calibration system accurately reproduces laboratory observing conditions for polarimeters.
• It is a promising tool for next-generation cosmic microwave background polarization experiments.
• Enhances the reliability and precision of CMB polarization data analysis.