[time-nuts] GENIUS by Stephen Hawking (PBS TV),

[Richard (Rick) Karlquist]

On 5/21/2016 8:37 AM, ws at Yahoo via time-nuts wrote:

> How would one go about to prove beyond a doubt in that experiment that 18ns
> of phase shift in 24 hrs was truly caused by freq offset due to Relativity
> and not by some other combination of environment and handling issues that
> effected phase &/or freq once the identical clocks where separated and
> operating at different temperatures, pressures, elevations, vibration, tilt
> angles, power supply voltages, airflow, cosmic rays, ozone, or some other
> unmeasured things that may be effecting the results?
>
> To increase  *gravity* a lot more than a 7,000 ft altitude change, and
> without changing the environment variables, could one set of the CS clocks
> be put on a centrifuge, such as a fast spinning merry-go-round at a local
> park?
>
> Anyone know what the 2G turn over effect, TC, etc, is of portable CS
> standards? Ideally they should all be zero, but probable aren't.
>
> ws
>

I was on the 5071A design team 25 years ago.  I designed most of the RF
sections.  We analyzed all known environmental effects (they were
known from experience with the 5061) and, using newer digital
technology, the individual effects where budgeted to better than
10^-14 each, and in most cases much better.  Len Cutler insisted!
It was refreshing to have a manager who didn't believe in "good enough".
This budgeting was to address ABSOLUTE accuracy.  We feel we proved
that absolute accuracy was mainly limited to end to end phase shift
in the Cs cavity.  Proprietary techniques were used to reduce this to
values equivalent to a mechanical asymmetry of a small fraction of a
"mil" (1/1000 inch).

Tom's experiment only requires STABILITY.  As you can see from Tom's
measurements vs an H maser, the Allan deviation is pure white noise
down to where the curves end at 10^-14.  Thus for sufficiently long
averaging time, the stability can be measured to this accuracy.
Even at this level, AD still has not "flickered out" meaning the
it would level off, and would not improve with additional time
averaging.

Various environmental tests were done with extremely long averaging
in an attempt to put a number on parameters such as tempco, humidity,
pressure, magnetic field, etc.  These tests took place over the
better part of a year.  The results were that none of these parameters
could be measured, because no effects were observed.  We could only
say that there was an upper bound in the area of 10^-15 on these
effects.

2G turnover is a special case.  Because the beam is a physical stream
of particles, it is possible that acceleration could affect the
beam.  Len Cutler discovered that previous HP cesium beam tubes
had a design flaw that made them have transient errors when used
in submarines (IOW they could get "seasick" :-).  I don't remember
exactly the details, but it was something like using dual beams,
that seemed like a good idea at the time, but had some sort of
physics fallacy.  Simply mounting the standard upside down vs
right side up does not create any error as it does in a crystal
oscillator.  I believe that the perfected design was also immune
to the act of flipping it over, carrying it around, or driving
around in a car with it.  I don't know about a centrifuge.  At
some point, the internal OCXO error will not be correctable
by the slow feedback loop.  Let's be reasonable here.

In any event, event the original 5060A flying clock trips made
by Cutler himself survived baggage handlers (who I am sure were
on their best behavior under Len's watchful eye.)  The 5071A is
light years ahead of that design, with virtually everything
under closed loop control.

We felt that we did as well as was possible for a non-reversible
cavity of that size, without optical pumping.  Not to mention
that it runs on an internal lead acid battery (this was before Li Ion) 
and can be lifted by one (strong) person.

It was great to see that this clock is still relevant as it nears
its 25th birthday.

Rick Karlquist N6RK