太阳低频射电干涉阵的构建仿真

介绍了低频射电干涉阵的发展情况、研究领域,讨论了国际上的LOFAR、LWA和MWA等低频射电项目.借鉴当今的低频射电项目,结合云南的地理和太阳射电优势,设想在云南省内构建一个太阳低频射电干涉阵,观测频率在30 MHz～250 MHz范围内,文中仿真了太阳低频射电干涉阵(4台站),比较和分析了通过优化算法得到的阵列的UV覆盖、脏束(Dirty beam);讨论了低频射电干涉阵的观测模式、射电干扰、低频射电成像等问题;分析低频射电阵在观测太阳爆发性活动产生的日冕物质抛射(Coronal Mass Ejections,CME)、耀斑、射电爆发的可能性;通过上述的仿真和分析构建太阳低频射电干涉阵面临的问题,可以为今后建立阵列提供依据.     

基于RASCIL的W-projection和W-stacking并行算法实测研究

在射电干涉阵的大视场成像中,W-projection和W-stacking是两类主要成像方法,本文对这两种成像方法进行了并行实测研究。首先分析了两种成像方法的基本原理框架,在此基础上对两种成像方法并行实现的关键因素进行讨论和分析。利用已经校准的射电干涉阵观测数据对两种成像方法基于射电天文模拟、校准和成像库(Radio Astronomy Simulation, Calibration, and Imaging Library, RASCIL)分别进行并行策略研究和并行计算实验。通过对并行计算时间、并行效率和并行资源配置模式的分析,得到了两种成像方法基于RASCIL(https://gitlab.com/ska-telescope/external/rascil)的并行计算性能,结果表明,两种成像方法都适合采用Strong Scaling的并行资源配置模式进行并行计算,基于RASCIL的W-stacking并行计算还有比较大的性能提升空间。     

射电干涉阵GPU相关器的研究初探

射电干涉仪阵列规模的不断扩大使其观测能力越来越强,但与之俱来的密集型数据的实时处理对传统解决方案的性能和成本等带来巨大的挑战,针对该挑战设计并验证了GPU解决方案。首先着重分析了射电干涉仪的相关器在运算和传输等方面的基本需求,然后根据射电干涉阵列信号的特征,尝试了多种GPU相关器模型,通过将相关器的计算任务有效映射为GPU线程模型,显著提高了GPU的利用率,使单GPU的实际计算性能达到了理论峰值性能的77%。最后以我国正研制的天籁计划为依托,开展了多种关键技术的先导实验,为进一步在GPU集群环境下针对大型射电干涉仪的需求研发一套同时兼备成本低、性能高、功耗少等优势的相关器打下了坚实的基础。     

光学综合孔径干涉成像的关键技术及多光束干涉仿真

闭合相位技术、U -V覆盖技术和像重构技术是光学综合孔径干涉成像的三个关键技术。文中简要介绍了光学综合孔径技术的发展历史、这三种关键技术和光学综合孔径望远镜阵的构成 ,对之进行了多光束干涉的计算机仿真和实验仿真 ,两者结果一致说明了光学综合孔径干涉成像技术中有关干涉的理论的正确性 ,指出了下一步的研究方向。     

天文光干涉与综合孔径技术的发展

本文简单介绍了光干涉与综合孔径技术发展的历史、国际上用于天文观测的一些著名光干涉仪的技术特点和进展、以及近年来我国开展的与光干涉 ,综合孔径技术有关的工作 ,最后简要介绍了在光学综合孔径技术领域所发展的光纤与集成光学等新技术     

基于分布式执行框架的低频射电干涉阵列成像管线优化

平方公里阵列(Square Kilometre Array,SKA)项目是建设全球最大射电望远镜的国际合作项目,其灵敏度和测量速度将比当前所有的射电望远镜都要高出一个数量级.连续谱巡天是SKA的主要观测模式之一,基于连续谱成像建立巡天区域的标准星图,将能为后续天文科学研究奠定重要基础.银河系与河外星系全天默奇森宽场阵列拓展巡天(GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended,GLEAM-X)是2018—2020年利用SKA先导望远镜默奇森宽场阵列(Murchison Wide-field Array,MWA)二期拓展阵列开展的新的射电连续谱巡天项目,观测期间积累了大量的低频巡天观测数据.海量观测数据的自动化、大批量处理是SKA望远镜项目所面临的的最大挑战和难题之一,基于分布式执行框架的成像管线优化经验将有助于解决海量数据处理问题.详细介绍了GLEAM-X成像管线并对其进行整合和改进,在中国SKA区域中心原型机(China SKA Regional Centre Prototype,...     

综合孔径干涉望远镜的高分辨率图像重建

利用干涉望远镜成像,可以获取最长基线对应的高频率信息,但往往只能获得部分频域覆盖.为了获得尽可能多的频率信息,可以先通过孔径排布变换,进行更充分的频率采样,再经过干涉图像合成,得到含有完备频率信息的目标高分辨率重建像.介绍了综合孔径干涉望远镜的高分辨率图像重建工作,重点讨论了孔径旋转条件下的干涉图像对齐和合成问题,并成功实施了天文目标的干涉成像观测实验,获得了有完备频率信息的目标高分辨率重建像.     

射电干涉测量对天文脉泽研究的贡献

天文脉泽已成为一个迅速的研究领域，重点评述了射电干涉测量对天文脉泽观测和研究所起的作用。     

Array Signal Processing for Radio Astronomy

Radio astronomy forms an interesting application area for array signal processing techniques. Current synthesis imaging telescopes consist of a small number of identical dishes, which track a fixed patch in the sky and produce estimates of the time-varying spatial covariance matrix. The observations sometimes are distorted by interference, e.g., from radio, TV, radar or satellite transmissions. We describe some of the tools that array signal processing offers to filter out the interference, based on eigenvalue decompositions and factor analysis, which is a more general technique applicable to partially calibrated arrays. We consider detection of interference, spatial filtering techniques using projections, and discuss how a reference antenna pointed at the interferer can improve the performance. We also consider image formation and its relation to beamforming.     

Probing Statistical Isotropy of Cosmological Radio Sources using Square Kilometre Array

There currently exist many observations which are not consistent with the cosmological principle. We review these observations with a particular emphasis on those relevant for the Square Kilometre Array (SKA). In particular, several different data sets indicate a preferred direction pointing approximately towards the Virgo cluster. We also observe a hemispherical anisotropy in the Cosmic Microwave Background radiation (CMB) temperature fluctuations. Although these inconsistencies may be attributed to systematic effects, there remains the possibility that they indicate new physics and various theories have been proposed to explain them. One possibility, which we discuss in this review, is the generation of perturbation modes during the early pre-inflationary epoch, when the Universe may not obey the cosmological principle. Better measurements will provide better constraints on these theories. In particular, we propose measurement of the dipole in number counts, sky brightness, polarized flux and polarization orientations of radio sources. We also suggest test of alignment of linear polarizations of sources as a function of their relative separation. Finally we propose measurement of hemispherical anisotropy or equivalently dipole modulation in radio sources.     

A Fast Radio Burst Backend for the Tianlai Dish Pathfinder Array

The Tianlai Dish Pathfinder Array is a radio interferometer array consisting of 16 six-meter dish antennas. The original digital backend integration time is at the seconds level, designed for H I intensity mapping experiment. A new digital backend with millisecond response is added to enable it to search for fast radio burst during its observations. The design and calibration of this backend, and the real time search pipeline for it are described in this paper. It is capable of forming 16 digita...     

三能级Tonks-Girardeau气体的Ramsey干涉的研究

采用Ramsey分离振荡场方法,研究了紧束缚一维强相互作用的超冷玻色气体在Tonks-Girardeau区的Ramsey干涉。在等失谐情况下,干涉条纹宽度随着原子与分离场作用时间和拉比(Rabi)频率的增大而变窄。对量子投影噪声的研究表明,相比二能级Tonks-Girardeau气体,对于三能级模型,通过控制原子总数和调节外场可以降低量子噪声,有效地减少噪声对Tonks-Girardeau气体系统的干扰。原子干涉的探索对提高量子频率标准的精度具有重要理论指导意义。     

Thirty-Element Active Antenna Array as a Prototype of a Huge Low-Frequency Radio Telescope

An effective wide-band (10 to 60 MHz) active antenna element has been developed. The cost of one short (3 m), thin dipole with built-in amplifier and metal construction is less than 45 euro. It was shown both theoretically and experimentally that the upper limiting frequency is at least 60 MHz, the dynamic range is 90 dB/V and the share of the amplifier noise to the background antenna temperature is about 10%. The developed active dipole was tested by building a 30-element antenna array and comparing its parameters with one of the subpart of the UTR-2 radio telescope having passive dipoles of 8.6 m in length and 1.8 m in diameter. The 3C461 ionospheric scintillation spectra observed in the experiments show that the sensitivities and noise-immunities of both antennas are close. This proves the availability using of a short cheap active dipole in new generation giant radio telescopes.     

A Study on the CdZnTe Array Detector

The CdZnTe array detector is a new type of semiconductor detector being rapidly developed in recent years. It possesses a high spatial resolution and a high energy resolution, and it can work at room temperatures. This paper describes the physical properties and working principle of the CdZnTe array detector, as well as the manufacturing technology, including the chip pretreatment, passivation, ohmic electrode preparation, array template selection, and array packaging technology (micro-interconnection). For evaluating the perfor-mance of the detector, the authors have developed successfully a 4 pixel×4 pixel CdZnTe array and an 8 pixel×8 pixel CdZnTe array (with the thicknesses of 5 mm and 2 mm, the pixel size of 2 mm×2 mm, and the gaps of 0.15 mm and 0.2 mm, respectively) in cooperation with the partner. A multi-channel electronic readout system based on the ASIC (Application Specific Integrated Circuit) chip is devel-oped independently for the charge measurement of the 4 pixel×4 pixel CdZnTe array. The energy spectra and corresponding energy resolutions of the 16 pixels are obtained with the ¹³⁷Cs radiative source, among them the best resolution is 4.8%@662 kev.