A Clock Stabilization System for CHIME/FRB Outriggers
A Clock Stabilization System for CHIME/FRB Outriggers
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DOI：
10.3847/1538-3881/ac397a
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发表时间：
2021-10
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通讯作者：
J. Mena-Parra;C. Leung;S. Cary;K. Masui;J. Kaczmarek;M. Amiri;K. Bandura;P. Boyle;T. Cassanelli;J. Cliche;M. Dobbs;V. Kaspi;T. Landecker;A. Lanman;J. Sievers
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作者：
J. Mena-Parra;C. Leung;S. Cary;K. Masui;J. Kaczmarek;M. Amiri;K. Bandura;P. Boyle;T. Cassanelli;J. Cliche;M. Dobbs;V. Kaspi;T. Landecker;A. Lanman;J. Sievers
加拿大氢强度测绘实验（CHIME）已经成为探测快速射电暴（FRB）的主要望远镜。CHIME/FRB支腿将是一个专用的甚长基线干涉测量（VLBI）仪器，由大陆基线的支腿望远镜组成，与CHIME及其专用的实时瞬态搜索后端（CHIME/FRB）合作，以50 mas的精度检测和定位FRB。在本文中，我们提出了一种微创的时钟稳定系统，有效地将CHIME数字后端参考时钟从其原来的GPS纪律烘箱晶体振荡器的被动氢脉泽。这使我们能够联合收割机相结合的长期稳定性和绝对时间标记的GPS时钟的微波激射器的短期和中期的稳定性，以减少VLBI校准观测之间的时钟定时误差。我们验证了系统与VLBI风格的观测天鹅座A超过400米的CHIME和CHIME探路者之间的基线，展示了基于天空和基于脉泽的定时测量之间的协议，在30 ps均方根水平的时间尺度从一分钟到九天，并满足CHIME/FRB支腿的稳定性要求。此外，我们提出了一个替代的参考时钟的解决方案，缺乏基础设施，以支持被动氢脉泽的外伸站。
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has emerged as the prime telescope for detecting fast radio bursts (FRBs). CHIME/FRB Outriggers will be a dedicated very-long-baseline interferometry (VLBI) instrument consisting of outrigger telescopes at continental baselines working with CHIME and its specialized real-time transient-search backend (CHIME/FRB) to detect and localize FRBs with 50 mas precision. In this paper, we present a minimally invasive clock stabilization system that effectively transfers the CHIME digital backend reference clock from its original GPS-disciplined ovenized crystal oscillator to a passive hydrogen maser. This enables us to combine the long-term stability and absolute time tagging of the GPS clock with the short- and intermediate-term stability of the maser to reduce the clock timing errors between VLBI calibration observations. We validate the system with VLBI-style observations of Cygnus A over a 400 m baseline between CHIME and the CHIME Pathfinder, demonstrating agreement between sky-based and maser-based timing measurements at the 30 ps rms level on timescales ranging from one minute to up to nine days, and meeting the stability requirements for CHIME/FRB Outriggers. In addition, we present an alternate reference clock solution for outrigger stations that lack the infrastructure to support a passive hydrogen maser.