Background Imaging of Cosmic Extragalactic Polarization (BICEP): An Experimental Probe of Inflation

宇宙微波背景(CMB)提供了三个强有力但间接的证据，证明可见宇宙是由微小空间的超光速膨胀产生的：地平线的近各向同性、空间的平坦性和早期宇宙中声波振荡的相位同步。为了更好地理解宇宙的起源，需要直接探索这个通货膨胀的时代。对通货膨胀最有希望的探测是GWB在CMB的两极分化上留下的独特签名。这一信号的幅度取决于通货膨胀的能量尺度。如果能量尺度是典型的大统一理论(GUT)(10^153x10^16GeV)，那么信号可能是可检测到的。GWB激发极化的信号预计将小于CMB的均方根幅度~300nK；比最近才解决的温度各向异性的幅度低两个数量级以上。探测只需要适度的角分辨率(~1°)，但需要在有限的(~3%)和连续的天空中进行长时间的积分(~1年)。六个月的夜晚，极端干燥和稳定的天气，以及天空围绕天顶的精确旋转，使南极站成为这一雄心勃勃的计划的理想地球站点。目前正在建造一台CMB偏振仪(BICEP)，它是唯一能够探测GWB特征的仪器，将于2003年部署到南极。正在建造BICEP的团队包括四名成功地将尖端测辐射仪器部署到南极的资深实验者。二头肌将在100 GHz和150 GHz同时工作，以尽量减少和识别来自极化天体物理前景的混淆。在这些频率下，一个适中的(因此相对容易部署和维护的)20厘米主孔径将提供1度的分辨率。在100 GHz和0.7度。150 GHz。通过将为普朗克(2007年发射)开发的新的偏振敏感测辐射热探测器技术与四个独立级别的信号差分和精心优化的观测策略相结合，BICEP将在积分的第一个小时内达到当前对CMB偏振的限制，在第一周达到超过1%天空的Planck灵敏度，并在1度的关键角度尺度上精确测量CMB偏振。至10度。BIBEP将通过以下方式服务于更广泛的宇宙学家和天体物理学家群体：(I)在这一令人兴奋的新领域开创数量级的改进；(Ii)描述最终将限制这种类型的测量(并且与银河系天文学家直接感兴趣的)的弥漫的天体物理前景；(Iii)展示有望对毫米波偏振测量具有广泛重要性的新技术和方法；以及(Iv)在这方面有非常好的记录的实验室为研究生和博士后研究员提供出色的培训。观测宇宙学目前正在经历一场文艺复兴，激发了公众的想象力，并成为激发人们对科学感兴趣的最有效工具之一。在CMB中探测到GWB的签名将代表着基础物理学和宇宙学的胜利，这将彻底改变我们对宇宙起源的理解。

The Cosmic Microwave Background (CMB) provides three strong but circumstantial pieces of evidence that the visible Universe was created by the superluminal inflation of a tiny volume of space: the near isotropy of the horizon, the flatness of space, and the phase-synchronicity of acoustic oscillations in the early universe. The goal of better understanding the origins of the Universe requires probing this epoch of Inflation directly. The most promising probe of Inflation is the unique signature that the GWB imprints on the polarization of the CMB. The amplitude of this signature depends on the energy-scale of Inflation. If the energy scale is typical of Grand Unification Theory (GUT) (10^15 3 x 10^16 GeV), the signature may be detectable. The signature of the GWB-induced polarization is expected to be less than an rms amplitude of ~300 nK of the CMB; more than two orders of magnitude below the amplitude of the temperature anisotropies that have only recently been resolved. Detection will require only modest angular resolution (~ 1 deg.), but will require long integration (~1 year) on a restricted (~3%) and contiguous patch of sky. The six-month night, the extremely dry and stable weather, and the precise rotation of the sky about the zenith make South Pole Station the ideal terrestrial site for this ambitious project. A CMB polarimeter (BICEP) uniquely capable of detecting the signature of the GWB is now under construction and will be available for deployment to the South Pole in 2003. The team that is building BICEP includes four senior experimentalists who have successfully fielded sophisticated bolometric instrumentation to the Antarctic. BICEP will operate simultaneously at 100 and 150 GHz in order to both minimize and recognize confusion from polarized astrophysical foregrounds. At these frequencies, a modest (and thus relatively easy to deploy and maintain) 20-cm primary aperture will provide a resolution of 1deg. at 100 GHz and 0.7 deg. at 150 GHz. By combining a new polarization-sensitive bolometric detector technology developed for Planck (2007 launch) with four independent levels of signal differencing and a carefully optimized observing strategy, BICEP will reach the current limit on CMB polarization in the first hour of integration, reach the sensitivity of Planck over 1% of the sky in the first week, and precisely measure CMB polarization on the critical angular scales of 1 deg. to 10 deg. BICEP will serve the broader community of cosmologists and astrophysicists by (i) pioneering an orders-of-magnitude improvement in this exciting new field, (ii) characterizing the diffuse astrophysical foregrounds that will ultimately limit measurements of this type (and which are of direct interest to Galactic astronomers), (iii) demonstrating new technologies and methodologies that promise to be of broad importance to millimeter-wave polarimetry, and (iv) providing excellent training for graduate students and postdoctoral fellows in labs which have a very strong track-record in this regard. Observational cosmology is currently enjoying a renaissance that has captured the public imagination, and serves as one of the most effective vehicles for stimulating interest in science in general. Detection of the signature of the GWB in the CMB would represent a triumph of fundamental physics and cosmology that would revolutionize our understanding of the origins of the Universe.