[time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)
Ole Petter Ronningen
opronningen at gmail.com
Tue Nov 21 09:14:59 EST 2017
On Tue, Nov 21, 2017 at 2:50 PM, Attila Kinali <attila at kinali.ch> wrote:
> [...] The advantage of the platinum valve
> system is that it "generates" single atom Hydrogen, as required
> by the maser.
Picking nits here.. It was my understanding that the splitting of molecular
hydrogen into atomic hydrogen happens using RF in the dissociator - not in
the platinum leak valve. Is my understanding incorrect?
> Within the cavity there is a small glass bulb that keeps the atoms
> in the right position of the cavity field.
4.5 liters in EFOS type masers - so not *that* small. I believe other
masers are the same order of magnitude.
> Yes, IIRC normal numbers are several 10s to 100s of wall collisions
> before the atom loses its state due to wall colisions and without
> contributing to the signal.
Lifetime ~1 second I think
> > I've long wondered what causes the slow frequency drift, typically
> > to about 3E-14 over a time span of several months.
> Mostly changes in the wall coating leading to a different wall collision
> shift and mechanical changes of the cavity dimension (think air pressure
> and creep) leading to a different cavity pulling. To a lesser extend
> it's the changes in the quality of the vacuum and number of Hydrogen atoms
> in the cavity.
Also aging of electronic components - coarse tuning of the cavity is done
by temperature, and any drift if the temperature-sensor/amplifiers etc will
result in drift. At least for EFOS type masers.
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