High Efficiency Wideband Refractive Optics for ALMA Band-1 (35-52 GHz)
High Efficiency Wideband Refractive Optics for ALMA Band-1 (35-52 GHz)
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适用于 ALMA Band-1 (35-52 GHz) 的高效宽带折射光学器件
DOI：
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发表时间：
2016
期刊：
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通讯作者：
L. Bronfman
中科院分区：
文献类型：
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作者：
V. Tapia;Antonio G. González;R. Finger;F. Mena;D. Monasterio;N. Reyes;M. Sánchez;L. Bronfman
我们介绍了ALMA波段1的设计、实现和光学特性，这是最先进的射电天文望远镜中最低的频段。频带1覆盖了35至50 GHz的宽频率范围，目标是在52 GHz以内实现较小的退化。这是迄今为止所有ALMA波段中最大的分数带宽。由于光学是任何接收机的第一个子系统，低噪声系数和最大孔径效率是最佳灵敏度的基础。然而，几个因素（低温恒温器孔径小、机械约束和成本限制）的结合使得实现这些目标极具挑战性。为了克服这些问题，这里介绍的光学包括两个创新的解决方案，一个紧凑的优化轮廓波纹角和一个改进的菲涅耳透镜。对喇叭轮廓进行了优化，使其具有最佳的性能，并且易于在车床上进行单件制造。这样，与传统的制造方法相比，可制造性大大降低。为了最大限度地降低光学器件的噪声贡献，设计了一步式分区透镜。其参数经过精心优化，以最大限度地提高频率覆盖范围，减少损耗。这里报告的光学组件完全符合ALMA规范。
We present the design, implementation, and characterization of the optics of ALMA Band 1, the lowest frequency band in the most advanced radio astronomical telescope. Band 1 covers the broad frequency range from 35 to 50 GHz, with the goal of minor degradation up to 52 GHz. This is, up to now, the largest fractional bandwidth of all ALMA bands. Since the optics is the first subsystem of any receiver, low noise figure and maximum aperture efficiency are fundamental for best sensitivity. However, a conjunction of several factors (small cryostat apertures, mechanical constraints, and cost limitations) makes extremely challenging to achieve these goals. To overcome these problems, the optics presented here includes two innovative solutions, a compact optimized-profile corrugated horn and a modified Fresnel lens. The horn profile was optimized for optimum performance and easy fabrication by a single-piece manufacturing process in a lathe. In this way, manufacturability is eased when compared with traditional fabrication methods. To minimize the noise contribution of the optics, a one-step zoned lens was designed. Its parameters were carefully optimized to maximize the frequency coverage and reduce losses. The optical assembly reported here fully complies with ALMA specifications.