A Dual-Polarisation Receiver for Multi-Beam Interferometry

一种用于多光束干涉测量的双偏振接收器

• 批准号: 2285537
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2285537
• 关键词: Dual; Polarisation; Receiver; Multi; Beam

Interferometry in astronomy is a technique that employs an array of telescopes to obtain high spatial resolution and extremely detailed observation of stars, galaxies, molecular clouds, proto-planetary disk and other interesting stellar objects. In millimetre (mm) and sub-mm range, each of these telescopes is generally equipped with a heterodyne receiver that down-coverts the detected astronomical signal from several hundred GHz to a few GHz, so that the signal can be processed by standard electronics. To achieve high sensitivity for detecting extremely weak astronomical signals, these receivers require the employment of superconducting quantum mixers (SIS, Superconductor-Insulator-Superconductor detector) that need to be cooled below the transition temperature of the superconducting material (typically 4K). In addition, to recover the full signal strength, dual-polarization detection scheme is required to split the polarization of the incoming signal into two orthogonal polarization states, where each is detected via a separate SIS receiver chain, resulting in bulky and complicated receiver architecture. Due to this complexity, almost all the major mm/sub-mm facilities in the world, such as the Sub-Millimetre Array (SMA, Hawai'i) and the Atacama Large Millimetre/Sub-Millimetre Array (ALMA, Chile), have only one-pixel receiver equipped in each of the telescope. Installing more pixels however at the focal plane of each telescope (namely multiple-beam interferometry) will allow fast mapping of extended object such as nearby galaxies, that otherwise would have to be carried out with mosaicking of individual pointing. This is important as it will allow the astronomers to probe further and faster, improving our understanding of the planet, star and galaxies formation, one of the key research themes outlined by STFC. Dual polarisation receiver is also the key instrument in the B-mode Cosmic Microwave Background (CMB) experiment in search for the understanding of the origin of the Universe, another major research area within the STFC programme.The main objective of this project is to build a compact dual-polarization receiver that will allow the installation of several channels (pixels) in each telescope receiver without excessive requirements on the cryostat size or cooling power of existing telescopes. The key feature of this design is that the two SIS mixer chains will be integrated on a single chip and located in a single block, using a novel planar orthomode transducer (OMT) to split the polarization.The project will be carried out in collaboration with the Harvard-Smithsonian Centre for Astrophysics (CfA) at Cambridge, Massachusetts, US, with whom we will collaborate in all aspects of the receiver design and construction. The student will develop the compact dual-polarization SIS receiver operating around 230 GHz to demonstrate this pioneering technology for the first time in heterodyne receivers. The SIS mixer chip will be tested in the THz Detectors Laboratory at Oxford and the receiver will also be assembled here. Whence completed, the receiver will be transferred to CfA for further integration before shipping for installation in the focal plane of the SMA, an interferometer comprising eight movable 6-meter diameter telescope sited on the Mauna Kea of Hawai'i. This receiver will also constitute a building block for the future construction of multi-pixel heterodyne receiver array and hence realizing multiple-beam interferometry for the SMA, and even ALMA once this technology is proven to be feasible.

天文学中的干涉测量是一种利用望远镜阵列来获得高空间分辨率和对恒星、星系、分子云、原行星盘和其他有趣的恒星物体进行极其详细的观察的技术。在毫米（mm）和亚毫米范围内，这些望远镜通常配备外差接收器，将检测到的天文信号从几百GHz下变频到几GHz，以便可以通过标准电子设备处理信号。为了实现检测极弱天文信号的高灵敏度，这些接收器需要使用超导量子混合器（SIS，超导-绝缘体-超导探测器），该混合器需要冷却到超导材料的转变温度（通常为 4K）以下。此外，为了恢复完整的信号强度，需要双偏振检测方案将输入信号的偏振分成两个正交的偏振状态，其中每个偏振状态都通过单独的SIS接收器链进行检测，从而导致接收器架构庞大且复杂。由于这种复杂性，世界上几乎所有主要的毫米/亚毫米设施，例如亚毫米阵列（SMA，夏威夷）和阿塔卡马大型毫米/亚毫米阵列（ALMA，智利），每个望远镜中仅配备一个像素接收器。然而，在每个望远镜的焦平面上安装更多像素（即多光束干涉测量法）将允许快速绘制扩展物体（例如附近的星系），否则必须通过单独指向的镶嵌来进行。这很重要，因为它将使天文学家能够进一步更快地探索，提高我们对行星、恒星和星系形成的理解，这是 STFC 概述的关键研究主题之一。双偏振接收器也是 B 模式宇宙微波背景（CMB）实验中的关键仪器，该实验旨在了解宇宙的起源，这是 STFC 计划中的另一个主要研究领域。该项目的主要目标是建造一个紧凑的双偏振接收器，允许在每个望远镜接收器中安装多个通道（像素），而不会对现有的低温恒温器尺寸或冷却功率提出过高要求。 望远镜。该设计的主要特点是两个 SIS 混频器链将集成在单个芯片上并位于单个模块中，使用新型平面正模传感器 (OMT) 来分离偏振。该项目将与美国马萨诸塞州剑桥市的哈佛-史密森天体物理中心 (CfA) 合作开展，我们将在接收器设计和建造的各个方面与该中心合作。该学生将开发工作频率约为 230 GHz 的紧凑型双极化 SIS 接收器，以首次在外差接收器中展示这一开创性技术。 SIS 混频器芯片将在牛津太赫兹探测器实验室进行测试，接收器也将在这里组装。完成后，接收器将被转移到 CfA 进行进一步集成，然后运输安装在 SMA 的焦平面上，SMA 是一个干涉仪，由八个可移动的 6 米直径望远镜组成，位于夏威夷莫纳克亚山。该接收器还将成为未来构建多像素外差接收器阵列的构建块，从而实现 SMA 的多光束干涉测量，一旦该技术被证明是可行的，甚至可以实现 ALMA。