International Research Fellowship Program: High Precision Measurement of the Polarization Anisotropy of the Cosmic Microwave Background Radiation

约翰森国际研究奖学金计划使美国科学家和工程师能够在国外进行三到二十四个月的研究。该计划的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项将支持布拉德利·R·约翰逊博士与威尔士大学卡夫兰分校的沃尔特·吉尔博士合作的为期22个月的研究奖学金。最近对MAXIMA和WMAP等实验产生的宇宙微波背景辐射(CMB)温度各向异性的测量表明，我们生活在一个由冷暗物质和宇宙常数主导的绝热膨胀宇宙学描述的宇宙演化中。鉴于这一事实，CMB应该是部分线偏振的，天空中的矢量场由无旋度(E模)分量和无散度(B模)分量组成。E模分量主要由标量扰动引起的复合时原始等离子体中的整体运动产生；B模分量是由膨胀重力波引起的张量扰动产生的。测量原始B模偏振的角功率谱将得出膨胀的能量标度。B.R.约翰逊是加的夫威尔士大学仪器小组的一员，致力于开发偏振仪器，用于对CMB的偏振进行高精度测量。该仪器将专门设计用于表征预期的B模式信号。原始的B型信号非常微弱，因此很难检测到。可能的仪器设计将使用数百个光子噪声受限的300MK测辐射热探测器，一个大到足以在150 GHz提供~5弧分分辨率的~2m反射望远镜，以及偏振调制硬件。一旦建造、集成和部署，该实验将在南极洲圆顶C的500平方度的天空区域绘制地图，在那里大气的毫米波辐射最小。

0402098JohnsonThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-two month research fellowship by Dr. Bradley R. Johnson to work with Dr. Walter Gear at the University of Wales in Cardiff.Recent measurements of the temperature anisotropy of the cosmic microwave background radiation (CMB) from experiments like MAXIMA and WMAP suggest we live in a universe whose evolution is described by adiabatic inflationary cosmology dominated by cold dark matter and a cosmological constant. Given this fact, the CMB should be partially linearly polarized with the vector field on the sky consisting of a curl-free (E-mode) component and a divergence-free (B-mode) component. The E-mode component was predominantly produced by bulk motion in the primordial plasma at recombination arising from scalar perturbations; the B-mode component was produced by tensor perturbations resulting from inflationary gravity waves. A measurement of the angular power spectrum of the primordial B-mode polarization will yield the energy scale of inflation. B. R. Johnson is working as part of the Instrumentation Group at the University of Wales, Cardiff to develop polarimetric instrumentation for making high precision measurements of the polarization of the CMB. This instrument will be specifically designed to characterize the anticipated B-mode signals. The primordial B-mode signal is extremely faint and therefore difficult to detect. Likely instrument designs will employ hundreds of photon noise limited 300 mK bolometric detectors, a ~2 m reflecting telescope large enough to provide ~5 arcmin resolution at 150 GHz, and polarization modulation hardware. Once constructed, integrated and deployed, the experiment will be map ~500 square degree regions of the sky from Antarctica at Dome C where the millimeter-wave emission of the atmosphere is minimized.