Back in November 2021 IEEE Spectrum published this article.
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You can get a very low jitter clock out of whispering-gallery mode oscillator made with a big lump of sapphire cooled to about 6K.It's big and expensive, but it the US National Ignition Facility wanted to synchronise 192 laser outputs, it would be a good place to start.
John Larkin's time delay generators couldn't exploit it.
The system I put together in 1988 for a stroboscopic electron beam generator could have. It would need a lot of upgrading to take full advantage of the sapphire oscillator, but we've had thirty years of faster logic and faster mixed signal devices to exploit for that.