A Precision Measurement of the Polarization of the 2.7K Cosmic Microwave Background Radiation

摘要9318727最近对2.7K宇宙微波背景辐射的光谱和空间各向异性的测量极大地提高了我们对早期宇宙的理解。这种辐射的第三个特征，即它的偏振，还没有被精确地测量出来。线偏振的幅度及其角相干长度对各向异性(密度微扰或引力波)的来源和宇宙的电离历史都非常敏感。预测的极化幅度是在7或T/T110-6的COBE/DMR各向异性信号大小的10%。这笔赠款将支持执行针对该角度尺度和更小范围进行优化的第一次测量。它将使用新的接收器技术，比以前的偏振实验灵敏度高100倍，以及一种新的仪器设计。在这种规模下，预计将达到比目前上限低约100倍的系数。改进的上限，或极化的检测将有助于：确定大规模各向异性是由密度扰动还是由引力波产生的确定复合是否是瞬时的确定再电离的红移研究各向异性与极化的相关性约束CMBR的可能的替代极化来源，如轴子、宇宙弦和纹理该项目将测量CMBR的极化，首先是大角度尺度(7)，然后是小尺度(1)。两个专门针对这两种测量进行优化的新型偏振仪正在建造中。它们将工作在两个不同的毫米波长，以抑制来自同步辐射的前景发射，并具有严格控制的系统效应和达到预期信号电平所需的高灵敏度。***

ABSTRACT 9318727 Timbie Recent measurements of the spectrum and the spatial anisotropy of the 2.7K Cosmic Microwave Background Radiation (CMBR) have dramatically improved our understanding of the early universe. The third characteristic of this radiation, its polarization, has not been measured as precisely. The amplitude of the linear polarization and its angular coherence length are extremely sensitive to both the source of anisotropy (density perturbations or gravitational waves) and the ionization history of the universe. The predicted polarization amplitude is 10% of the size of the COBE/DMR anisotropy signals at 7, or T/T110-6. This grant will support o perform the first measurements optimized for this angular scale and smaller. It will use new receiver technology with 100 times more sensitivity than previous polarization experiments, as well as a novel instrument design. It is expected to reach a factor of about 100 below present upper limits at this scale. An improved upper limit, or detection of polarization will help to: determine whether the large-scale anisotrophies were generated by density perturbations or by gravitational waves determine if recombination was instantaneous determine the redshift of reionization study the correlation of anisotropy with polarization constrain possible alternative sources of polarization of the CMBR such as axions, cosmic strings, and textures The project will measure CMBR polarization, first at large angular scales (7) and later at smaller scales (1). Two novel polarimeters optimized specifically for both measurements are being constructed. They will operate at two different millimeter wavelengths to reject foreground emission from synchrotron radiation and feature strictly- controlled systematic effects and the high sensitivity required to reach the expected signal level. ***