The Sunyaev-Zeldovich infrared experiment: A millimeter-wave receiver for cluster cosmology

Measurements of the Sunyaev-Zeldovich (S-Z) effect toward distant clusters of galaxies can be used to the Hubble constant and the radial component of cluster peculiar velocities. Determination of the cluster peculiar velocity requires the separation of the two components of the S-Z effect, which are due to the thermal and bulk velocities of the intracluster plasma. The two components can be separated practically only at millimeter wavelengths. Measurements of the S-Z effect at millimeter wavelengths are subject to minimal astrophysical confusion and, therefore, provide an important test of results obtained at longer wavelengths. We describe the instrument used to make the first significant detections of the S-Z effect at millimeter wavelengths. This instrument employs new filter, detector, and readout technologies to produce sensitive measurements of differential sky brightness stable on long timescales. These advances allow drift-scan observations that achieve high sensitivity while minimizing common sources of systematic error.