[time-nuts] Cold Rubidium?

[Anders Wallin]

This paper from the french group has some details
https://arxiv.org/pdf/1812.01658.pdf
they say it's a redesign of the previous version (
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.82.033436), but it
looks roughly the same..
page 2 of the datasheet shows the vacuum system and bulb:
https://www.muquans.com/wp-content/uploads/2019/03/muquans_muclock.pdf

from what I understand in the French design the Ramsey interrogation is
with a pulsed microwave source in the cavity.
the fact that the atoms fall down during interrogation, when cooling is
switched off, is not useful or significant at all(?)
the US design is maybe more like a fountain with two interrogation-zones
and the atoms fall through them?




On Sun, Oct 27, 2019 at 2:14 AM Michael Wouters <michaeljwouters at gmail.com>
wrote:

> The atoms are laser cooled and held in a magneto-optical trap. It’s
> basically a short, one-way fountain.
>
> Cooling the microwave cavity would be useful for reducing the black body
> radiation shift, but without checking the numbers, this would not be so
> useful at the relatively low accuracy claimed for the clock. Otherwise,
> it’s pretty much irrelevant to the atom temperature. It’s all UHV, so
> there’s no time to come to thermal equilibrium with whatever residual gas
> is in the vacuum enclosure.
>
> NIST used to operate a mercury ion microwave clock at cryogenic
> temperatures.
>
> Cheers
> Michael
>
> On Sun, 27 Oct 2019 at 8:01 am, Dana Whitlow <k8yumdoober at gmail.com>
> wrote:
>
> > I can only answer one of your questions with any confidence, but I'd
> > suspect that the
> > chamber walls are cooled a fair bit in addition to being highly
> > reflective.  Your other
> > questions age very good ones, too, and I'm looking forward to *somebody*
> > answering
> > them.  I'd also love to hear the details of how they go about
> interrogating
> > that cloud of
> > cold Rb atoms in such a short time (< 100 msec).
> >
> > Dana
> >
> >
> > On Sat, Oct 26, 2019 at 3:01 PM Richard (Rick) Karlquist <
> > richard at karlquist.com> wrote:
> >
> > > The proverbial "dumb questions":
> > >
> > > Is there an actual refrigerator somewhere
> > > in this gadget, or are the Rb atoms in a
> > > room temperature vacuum and the laser cools
> > > just the atoms.  It appears to be the latter.
> > >
> > > So the enclosure has low emissivity so it
> > > doesn't transfer too much heat to the atoms
> > > by radiation?
> > >
> > > And is it correct that the atoms are not ionized
> > > to trap them because the laser does that?
> > >
> > > Rick N6RK
> > >
> > > On 10/26/2019 1:39 AM, Anders Wallin wrote:
> > > > ptti2018:
> > > >
> > >
> >
> https://www.researchgate.net/publication/322920519_Long_term_frequency_instability_of_a_portable_cold_87Rb_atomic_clock
> > > > ifcs2018:
> > > >
> > >
> >
> https://www.researchgate.net/publication/325499937_A_portable_cold_87_Rb_atomic_clock_with_frequency_instability_at_one_day_in_the_10-15_range
> > > >
> > > > this one is apparently a darpa/spectradynamics/nist effort, and
> > there's a
> > > > similar story with muquans and syrte in france, see:
> > > > https://www.muquans.com/product/muclock/
> > > >
> > > >
> > > > On Fri, Oct 25, 2019 at 11:09 PM AC0XU (Jim) <
> > James.Schatzman at ac0xu.com>
> > > > wrote:
> > > >
> > > >> Does anyone have any experience/first hand knowledge of this Cold
> > > Rubidium
> > > >> standard?
> > > >>
> > > >> <https://spectradynamics.com/products/crb-clock/>
> > > >> https://spectradynamics.com/products/crb-clock/
> > > >>
> > > >> The specs look very good. The mfr claims that, unlike traditional
> > > rubidium
> > > >> oscillators, it has no long-term drift.
> > > >> Thanks!
> > > >> Jim
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