Research Objectives:
The Arcminute Cosmology Bolometer Array Receiver (ACBAR) is a 16 element 240 mK bolometer array designed for observations of small angular scale fluctuations in the Cosmic Microwave Background (CMB). Mounted on the Viper telescope at the South Pole, ACBAR produces high signal to noise images of the CMB with angular resolution of about 4 minutes. Due to the high sensitivity and resolution of the experiment, ACBAR provides a unique compliment to the large-scale CMB anisotropy maps and helps to improve constraints on models describing our Universe. ACBAR is presently observing in three millimeter-wavelength bands.
In the 2004-2005 austral summer, ACBAR will be retrofitted with sixteen 2.1 millimeter detector channels. The upgraded instrument will observe through the winter season in order to produce improved observations of fine scale CMB anisotropy. These new observations will be used to improve constraints on the matter density in the Universe and spectral index of the primordial matter fluctuations. Observations on the smallest angular scales will search for the signature of evolving galaxy clusters and produce constraints on the normalization of matter density fluctuations.
ACBAR will be removed from the Viper telescope when the project team arrives at the Pole shortly after station opening. The instrument will be brought into the MAPO building where it will be opened and refurbished.
The unique capabilities of ACBAR, which was deployed to the South Pole in December 2000, allow it to address a broad range of science focused on measuring primary and secondary CMB anisotropies. Our observations and analysis will help realize the full potential of this powerful instrument for the study of cosmology. Four institutions will continue to collaborate in the maintenance and operation of ACBAR and Viper and participate in the data analysis.
The results will serve as a vital complement to the large-scale Microwave Anistropy Probe (MAP) spacecraft data set and provide an essential check of the fine-scale excess power reported by other single-frequency experiments. The novel instrumentation, observation techniques, and analysis developed for ACBAR are generally applicable to future ground-based millimeter astronomy experiments. In addition, this project has provided hands-on research experience to several undergraduate and graduate students.
