[LEAPSECS] preprint about timekeeping for neutrino experiment
zefram at fysh.org
Tue Oct 4 07:04:03 EDT 2011
Fran?ois Meyer wrote:
>In my view the two clocks are just synced to each other as far as this experiment
>is concerned. That does not change the point about gravitation though.
I emailed Contaldi about the TTD, and I've just had this interesting
response from him:
Carlo Contaldi wrote:
|thanks for the comments, I corresponded with the OPERA group and I agree
|that the TTD is not a moving clock as I interpreted. However it is used
|to calibrate a relative delay at both ends of the baseline using local
|reference frequency generators and these would be susceptible to time
|dilation effects as in the stationary part of my calculations.
|In addition the time scales over which they calculate the delays are
|vastly different from those used in the measurement and it is not clear
|at all that they have measured the noise on the relevant time scales.
|Effectively they are relying on the GPS signal at both ends being
|synchronised at < ns and this is what I find hard to believe,
|particularly on short time scales where atmospheric effects may induce a
|much larger uncertainty than they have accounted for.
|I also agree that their Euclidean analysis may also introduce further
So I think the state of play is: need more details from the OPERA team,
and there's a world of error budget haggling to come.
I couldn't figure out the operation of the time source system (local
caesium plus GPS plus other bits) from the diagram in the PTB tech note.
The details seem to matter quite a bit to the synchronisation. Does
someone here know the equipment, or recognise the configuration? TvB?
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