The millimeter-wave bolometric interferometer

Abstract

The Millimeter-Wave Bolometric Interferometer (MBI) is designed for sensitive measurements of the polarization of the cosmic microwave background (CMB). MBI combines the differencing capabilities of an interferometer with the high sensitivity of bolometers at millimeter wavelengths. It views the sky directly through corrugated horn antennas with low sidelobes and nearly symmetric beam patterns to avoid spurious instrumental polarization from reflective optics. The design of the first version of the instrument with four 7-degree-FOV corrugated horns (MBI-4) is discussed. The MBI-4 optical band is defined by filters with a central frequency of 90 GHz. The set of baselines determined by the antenna separation makes the instrument sensitive to CMB polarization fluctuations over the multipole range l=150-270. In MBI-4, the signals from antennas are combined with a Fizeau beam combiner and interference fringes are detected by an array of spider-web bolometers with NTD germanium thermistors. In order to separate the visibility signals from the total power detected by each bolometer, the phase of the signal from each antenna is modulated by a ferrite-based waveguide phase shifter. Observations are planned from the Pine Bluff Observatory outside Madison, WI.

Modeling the quasi-optical performance of CMB astronomical interferometers

“…The Millimeter-Wave Bolometric Interferometer is a Fizeau interferometer that uses cooled spider web bolometers for detectors, combining the advantages of interferometry for control of systematic effects with the high sensitivity and frequency coverage possessed by bolometers [6]. It is the first bolometric interferometer of its kind which results in a novel instrument with capabilities that would be difficult to achieve using more traditional techniques and will allow MBI and instruments based on its technology to explore a wide range of angular scales and wavelengths.…”

Quasi-optical design and analysis of the millimeter-wave bolometric interferometer (MBI)

“…MBI is a ground-based telescope designed to make measurements of the polarization of the CMB at degree angular scales at a frequency of 90GHz. It is a Fizeau interferometer that uses cooled spider web bolometers for detectors, combining the advantages of interferometry for control of systematic effects with the high sensitivity and frequency coverage possessed by bolometers [5]. It is the first bolometric interferometer of its kind which results in a novel instrument with capabilities that would be difficult to achieve using more traditional techniques and will allow MBI and instruments based on its technology to explore a wide range of angular scales and wavelengths.…”