标题： RHINO：用于探测21厘米全局信号的大口径horn天线 显示英文标题

标题： RHINO: A large horn antenna for detecting the 21cm global signal

摘要： 中性氢的21厘米线的全天平均亮度温度提供了探测星系间介质热状态的灵敏探针，尤其是在宇宙黎明和再电离时期之前及期间。 这个“全局信号”非常微弱，大约在几十到几百毫开尔文之间，并且光谱相对平滑，这使得它极难从前景射电发射和仪器伪影中分离出来。 在这篇论文中，我们介绍了RHINO实验，该实验基于一个工作频率范围为60-85 MHz的大喇叭天线。 喇叭天线具有高度可表征性，并能提供良好的环境屏蔽，在这种实验特有的波束测量和建模问题上，这可能是决定性的优势。 该系统还包括一种新型连续波校准源，用于控制相关的增益波动，从而无需在天空和校准源之间快速切换即可持续监测整体增益水平。 在这里，我们描述了基本的RHINO概念，包括天线设计、电磁模拟以及接收机电子设备。 我们使用一个基本的模拟和分析管道来研究带宽限制对恢复物理21厘米全局信号模型参数的影响，并讨论了一种包含连续波信号的基本校准方案。 最后，我们报告了正在Jodrell Bank天文台建造的缩小原型系统的当前状态。 显示英文摘要

摘要： The sky-averaged brightness temperature of the 21cm line from neutral hydrogen provides a sensitive probe of the thermal state of the intergalactic medium, particularly before and during Cosmic Dawn and the Epoch of Reionisation. This `global signal' is faint, on the order of tens to hundreds of millikelvin, and spectrally relatively smooth, making it exceedingly difficult to disentangle from foreground radio emission and instrumental artefacts. In this paper, we introduce RHINO, an experiment based around a large horn antenna operating from 60-85 MHz. Horn antennas are highly characterisable and provide excellent shielding from their immediate environment, which are potentially decisive advantages when it comes to the beam measurement and modelling problems that are particularly challenging for this kind of experiment. The system also includes a novel continuous wave calibration source to control correlated gain fluctuations, allowing continuous monitoring of the overall gain level without needing to rapidly switch between the sky and a calibration source. Here, we describe the basic RHINO concept, including the antenna design, EM simulations, and receiver electronics. We use a basic simulation and analysis pipeline to study the impact of the limited bandwidth on recovery of physical 21cm global signal model parameters, and discuss a basic calibration scheme that incorporates the continuous wave signal. Finally, we report on the current state of a scaled-down prototype system under construction at Jodrell Bank Observatory.