[time-nuts] Time Dilation tinkering
Tom Van Baak
tvb at LeapSecond.com
Tue Mar 21 22:03:13 EDT 2017
Yes, MAC and CSAC do show environmental sensitivity. But that should not be a surprise to anyone that works with precise time & frequency.
The factors include voltage, temperature, temperature gradient, pressure, humidity, acceleration, tilt (orientation), and who knows what else. Maybe even radiation? One looks for the *coefficient* of course, but also linearity, repeatability, hysteresis, and even interaction amongst factors. It's not an easy task to do this, nor can one assume each unit of a given make/model will be the same. I don't have comprehensive data or a nice report.
But attached is one of the first plots where I put a SA.32m in a home-brew vacuum chamber and pulled down to a few inches of Hg for a few hours to simulate the low pressure of a flight up to 50 or 90,000 ft. For a high altitude relativity experiment -- where you'd like your clock to remain stable to parts in e-13 and not accumulate too many stray ns -- it's not a good sign when your clock changes by 2e-11 (that's more than 1 ns per minute) just because of ambient pressure changes.
Of course some of you are thinking: use isolation, regulation, and live or even post-processed compensation mechanisms. If someone seriously wants to pursue the CSAC / balloon concept contact me off-list. A fair amount of work went into it before we pulled the plug. I watched enough HAB (high altitude balloon) videos to make me ill. For our precious nanoseconds, it is a very hostile environment up there.
Maybe let's take this thread off-list.
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