用于精确测量Sunyaev-Zel'dovich效应的高效差分傅里叶变换光谱仪
Efficient Differential Fourier-Transform Spectrometer for precision Sunyaev-Zel'dovich effect measurements
摘要：
精确测量星系团中的Sunyaev-Zel'dovich效应需要出色的共模信号抑制和宽频率覆盖范围。我们描述了一种成像，高效，差分傅里叶变换光谱仪（FTS），在毫米波长的微弱亮度梯度的测量进行了优化。我们的仪器是基于马丁-普普莱特干涉仪（MPI）配置。我们将两个同步工作的MPI结合起来，以使用整个输入功率。在我们的实现中，所观察到的天空场沿子午线分为两半，每个半场对应于MPI的两个输入端口之一。通过这种方式，FTS焦平面中的每个探测器测量相对于子午线对称定位的两个天空像素之间的亮度差异。利用MPI的高共模抑制，我们可以测量高各向同性背景上的低天空亮度梯度。该仪器的工作范围$\sim$ 1 $-$ 20厘米$^{-1}$（30 $-$ 600 GHz），具有最大的光谱分辨率$1/(2 \ OPD) = 0.063 \ cm^{-1}$（1.9 GHz），和2.3厘米$^2$ sr的无晕吞吐量。它占用的体积为0.7 $\times$ 0.7 $\times$ 0.33米$^3$，并具有70公斤的重量。这种设计可以作为一个低温装置在空间使用，也可以作为一个室温装置在亚轨道和地面毫米波望远镜的焦点上工作。该仪器的第一次飞行测试是OLIMPO在平流层气球上进行的实验;正在为撒丁岛射电望远镜准备更大的实施。
英文摘要：
Precision measurements of the Sunyaev-Zel'dovich effect in clusters of galaxies require excellent rejection of common-mode signals and wide frequency coverage. We describe an imaging, efficient, differential Fourier transform spectrometer (FTS), optimized for measurements of faint brightness gradients at millimeter wavelengths. Our instrument is based on a Martin-Puplett interferometer (MPI) configuration. We combined two MPIs working synchronously to use the whole input power. In our implementation the observed sky field is divided into two halves along the meridian, and each half-field corresponds to one of the two input ports of the MPI. In this way, each detector in the FTS focal planes measures the difference in brightness between two sky pixels, symmetrically located with respect to the meridian. Exploiting the high common-mode rejection of the MPI, we can measure low sky brightness gradients over a high isotropic background. The instrument works in the range $\sim$ 1$-$20 cm$^{-1}$ (30$-$600 GHz), has a maximum spectral resolution $1/(2 \ OPD) = 0.063 \ cm^{-1}$ (1.9 GHz), and an unvignetted throughput of 2.3 cm$^2$sr. It occupies a volume of 0.7$\times$0.7$\times$0.33 m$^3$ and has a weight of 70 kg. This design can be implemented as a cryogenic unit to be used in space, as well as a room-temperature unit working at the focus of suborbital and ground-based mm-wave telescopes. The first in-flight test of the instrument is with the OLIMPO experiment on a stratospheric balloon; a larger implementation is being prepared for the Sardinia radio telescope.
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