Speaker
Description
In the recent years, Cherenkov telescopes have begun to be used for observations in the optical band using the technique of intensity interferometry. Intensity interferometry requires fast detectors—which Cherenkov telescopes already possess, as their cameras are comprised of photomultiplier tubes (PMTs)—as well as time synchronization between two telescopes to record data simultaneously and enable correlation either in real time or offline.
White Rabbit (WR) is employed for this synchronization, achieving sub-nanosecond accuracy. However, to further increase the signal-to-noise ratio (SNR) and detect fainter sources, even faster detectors are needed—for example, single-photon avalanche diodes (SPADs). These detectors are capable of detecting individual photons and generating corresponding pulses with overall jitter under 10 ps RMS. This imposes even stricter time synchronization requirements: the timing between two telescopes or detectors must match the SPAD-induced jitter, i.e., be below 10 ps.
WR, built upon the Precision Time Protocol (PTP), natively offers sub-nanosecond synchronization with deterministic latency. We demonstrate that a WR network can be efficiently shared between optical and Imaging Atmospheric Cherenkov Telescope (IACT) observatories for joint intensity interferometry observations. We investigate and address key challenges, including the effects of fiber temperature fluctuations and chromatic dispersion, which can impact long-distance timing stability.
Through experimental validation, we achieve 8 ps RMS time synchronization over a 50 km fiber link, demonstrating the feasibility of WR for high-precision astronomical applications. Furthermore, we analyze how WR clock phase coherence affects intensity interferometry sensitivity and discuss the implications for long-baseline and large-scale deployments.
