CAMELS - The Cambridge Emission Line Surveyor for the Greenland Telescope

人们普遍认为，发展成熟的芯片光谱仪技术，其中焦平面阵列中的每个像素本质上都能够产生详细的光谱信息，将给远红外和亚毫米波(4毫米至300微米)天文学带来革命性的变化。低光谱分辨率通道(R=5-20)可用于CMB和SZ天文观测，并可通过同时对连续谱源进行多色观测来确定尘埃温度；中光谱分辨率通道(R=500-1000)可用于大视场盲测高红移谱线；高光谱分辨率通道(R=2000-4000)可用于恒星形成区和扩展的附近星系的分子气体多线作图。一旦核心技术可用，大量像素可以被打包成阵列用于测绘和测量，或者少量像素可以稀疏地放置在大视场上，以实现多对象光谱分析。尽管许多组织正在研究芯片光谱仪，但国际社会还没有展示出科学级的观测结果。在某种程度上，这种情况的发生是因为在亚毫米波望远镜上需要大量的时间来了解行为和改进设计。为了解决这一问题，我们提出了一种适用于70-115 GHz(4.3-2.6 mm)大气窗口的高分辨率(R=3000)超导滤波器组光谱仪。剑桥发射线测量者(CAMELS)是卡文迪什实验室和哈佛史密森天体物理中心(CFA)的合作项目。骆驼将被安装在格陵兰望远镜上，并通过同时测量12CO(VR=115.271 GHz)和13CO(VR=110.201 GHz)谱线强度来绘制低Z星系的同位素丰度图。我们将评估两种略有不同的设计：一种是在高背景(NEP=2 x 10-17WHZ-1/2)的背景下绘制来自扩展星系(z=0.005-0.05)的亮线，另一种是在低背景(NEP=4 x 10-18WHZ-1/2)的情况下探测来自点源(z=0.05-0.12)的微弱线条。除了科学上的重要性，在70-115 GHz窗口的操作将允许我们探索性能，而不必担心大气造成的调度限制。芯片光谱仪的原理很容易理解，但实现一台能够进行科学级观测的完整仪器需要详细的知识。我们的像素将包括一个单模天线、一组超导射频滤波器、连接到一组动态电感探测器(KIDS)的终端，以及一条超导读出线。所有这些都将在使用多层超导微电路技术的单个晶片上实现。该芯片将使用快速数字电子技术和软件定义无线电(SDR)技术读出。剑桥集团运营着制造超导量子传感器的最先进设施，并在使用BCC-Ta、β-Ta、NbN、Nb、Al、Mo、Hf、Ir、Au、Cu、SiO、SiO、SiO在硅衬底和SiN膜上制造多层微电路方面拥有丰富的专业知识。这一设施将用于实现光谱仪模块。该技术的前景是可观的，我们的计划对STFC的愿景做出了巨大贡献。所有现有和计划中的地面和空间远红外观测站完全依赖超导成像阵列和接收器。超导器件处理技术现在已经成熟，下一步是生产具有复杂片上功能的微电路。例如，实现高光谱成像的能力将对未来空间望远镜的设计产生重大影响，其中每个像素都能够同时测量连续背景的温度和某些宽广空间线的强度。

It is widely recognised that the development of a mature chip spectrometer technology, where each pixel in a focal-plane array is intrinsically capable of yielding detailed spectroscopic information, would revolutionise far-infrared and submm-wave(4 mm to 300 um) astronomy. Low spectral-resolution channels (R = 5-20) could be used for CMB and SZ astronomy, and for determining dust temperatures through simultaneous multicolour observations of continuum sources; medium spectral-resolution channels (R = 500-1000) could be used for wide-field blind surveys of high-redshift spectral-lines; and high spectral-resolution channels (R = 2000-4000) could be used for multiline mapping of molecular gas in star-forming regions and extended nearby galaxies. Once the core technology is available, a large number of pixels could be packed into arrays for mapping and surveys, or a small number of pixels could be positioned sparsely over a wide field of view to enable multi-object spectroscopy. Although a number of organisations are working on chip spectrometers, the international community is falling short of demonstrating science-grade observations. To some extent this situation has occurred because a significant amount time is needed on a submm-wave telescope to understand behaviour and refine designs. To address this situation, we propose to demonstrate a high-resolution (R = 3000) superconducting filter-bank spectrometer for the 70-115 GHz (4.3-2.6 mm) atmospheric window. The Cambridge Emission Line Surveyor (CAMELS) is a collaborative project between the Cavendish Laboratory and the Harvard Smithsonian Center for Astrophysics (CFA). CAMELS will be installed on the Greenland Telescope (GLT) and used to map isotopic abundances in low-z galaxies by measuring 12CO (vr = 115.271 GHz) and 13CO (vr =110.201 GHz) line strengths simultaneously. We will assess two slightly different designs: One will map bright lines from extended galaxies (z = 0.005 - 0.05) against high backgrounds (NEP = 2 x 10-17 WHz-1/2), and the other will detect faint lines from point sources (z = 0.05 - 0.12) against low backgrounds (NEP = 4 x 10-18 WHz-1/2). As well as being scientifically important, operation in the 70-115 GHz window will allow us to explore performance, without worrying about scheduling limitations imposed by the atmosphere.The elements of a chip spectrometer are easy to understand in principle, but the realisation of a complete instrument that is capable of making science-grade observations requires detailed knowledge. Our pixels will comprise a single-mode antenna, a bank of superconducting RF filters, coupling terminations to an array of Kinetic Inductance Detectors (KIDs), and a single superconducting readout line. All of these will be realised on a single wafer using multi-layer superconducting microcircuit technology. The chip will be read out using fast digital electronics and Software Defined Radio (SDR) techniques. The Cambridge Group runs a state of the art facility for manufacturing superconducting quantum sensors, and has considerable expertise in fabricating multi-layer microcircuits using bcc-Ta, beta-Ta, NbN, Nb, Al, Mo, Hf, Ir, Au, Cu, SiO, SiO2 films on Si substrates and SiN membranes. This facility will be used to realize the spectrometer modules.The outlook for the technology is considerable, and our programme contributes strongly to STFC's vision. All existing and planned ground-based and space-borne far-infrared observatories are completely reliant on superconducting imaging arrays and receivers. Superconducting device processing technology is now well established, and the next step is to produce microcircuits having complex on-chip functionality. For example, the ability to realise hyperspectral imaging where each pixel is capable of measuring the temperature of the continuum background and the strengths of certain widely space lines simultaneously would have a major impact on the design of future space telescopes.