Precise synchronization of a free-running Rubidium atomic clock with GPS Time for applications in experimental particle physics

TL;DR

This paper develops a time correction algorithm to synchronize a free-running Rubidium atomic clock with GPS time, achieving better than 5 ns accuracy, crucial for experiments like Hyper-Kamiokande in particle physics.

Contribution

The study introduces a polynomial fitting method for real-time correction of Rubidium clock drift using GNSS signals, enhancing synchronization precision for scientific experiments.

Findings

Achieved synchronization within ±5 ns of GPS time.

Effective correction with a 10,000-second integration window.

Applicable to neutrino physics and astrophysics experiments.

Abstract

We present results of our study devoted to the development of a time correction algorithm needed to precisely synchronize a free-running Rubidium atomic clock with the Coordinated Universal Time (UTC). This R&D is performed in view of the Hyper-Kamiokande (HK) experiment currently under construction in Japan, which requires a synchronization with UTC and between its different experimental sites with a precision better than $100$ ns. We use a Global Navigation Satellite System (GNSS) receiver to compare a PPS and a $10$ MHz signal, generated by a free-running Rubidium clock, to the Global Positioning System (GPS) Time signal. We use these comparisons to correct the time series (time stamps) provided by the Rubidium clock signal. We fit the difference between Rubidium and GPS Time with polynomial functions of time over a certain integration time window to extract a correction of the Rubidium time stamps in offline or online mode. In online mode, the latest fit results are used for the correction until a new comparison to GPS Time becomes available. We show that with an integration time window of around $10^4$ seconds, we can correct the time stamps drift, caused by the frequency random walk noise and the deterministic frequency drift of the free running Rubidium clock, so that the time difference with respect to GPS Time stays within a $\pm5$ ns range in both offline or online correction mode. Presented results could be of interest for other experiments in the field of neutrino physics and multi-messenger astrophysics.