[time-nuts] Re: Creating a D.I.Y Rubidium Atomic Clock

[Leo Ahluwalia]

Hi Magnus, I appreciate the book suggestions, I'll have to take a look at
the primer and the books mentioned to hopefully get a clearer picture of
what my goals are. I hadn't realized that the package could be covered like
that (though I'm guessing post-construction for the most part), but it's
nice to hear that I won't have to set up a room or space for a dim-out.
I'll have to make sure to keep the timenuts posted once I've done some more
research.

Thanks, Leo

On Fri, Jun 9, 2023 at 8:08 AM Magnus Danielson via time-nuts <
time-nuts at lists.febo.com> wrote:

> Hi Leo,
>
> The physical package is wrapped such that essentially no ambient light
> comes in, the other design requirements drive the design that way
> anyway, both magnetic shielding and RF cavity, so I consider there being
> no need to do additional dim outs.
>
> You do not want to dim the photodetector itself fromt he light through
> rubidium. You already face a signal to noise problem there that will
> affect the stability.
>
> The Varnier and Audoin "The Quantum Physics of Atomic Frequency
> Standards" Vol 1 and 2 is very relevant too. These books are somewhat
> older, but great in depth reference. The Riley Rubidium Frequency
> Standard Primer is more modern, gives great orientation, but for some
> aspects do not go into more depth than necessary, which is fine, it is
> an excellent starting point that cover most issues, so read that first,
> and then dwell into Varnier and Audoin.
>
> Cheers,
> Magnus
>
> On 2023-06-08 18:45, Leo Ahluwalia via time-nuts wrote:
> > Hi Magnus, I'll definitely have to take a look at the resources Tom, zfe,
> > and Andy sent my way. To my theoretical knowledge, the attenuation of the
> > photo-detector is a possibility - to avoid having to dim out the room
> where
> > the apparatus is contained - and I was wondering if you or anyone else
> had
> > experience working with something of that nature. I appreciate the advice
> > on the setup, it definitely cleared up some things for me.
> >
> > - Leo
> >
> > On Wed, Jun 7, 2023 at 9:27 PM Magnus Danielson via time-nuts <
> > time-nuts at lists.febo.com> wrote:
> >
> >> Hi Leo,
> >>
> >> So, the setup is very straight forward. You put the Rb-lamp, the filter,
> >> the Rb resonance cell all lined up in a straight path and at the far end
> >> of that you have a photo-detector. The resonance cell you want to keep
> >> magnetically shielded, which is typically done by one or more (I have
> >> clocks with 3) layers of mu-metal. You have a coil, called C-field coil,
> >> through which a DC current creates a magnetic field that separates the 5
> >> Rb resonances so that only the (1,0)->(2,0) absorption occurs, which is
> >> detected by a thad lower intensity of the pump light.
> >>
> >> Look at Tom's email and I strongly suggest you get "Rubidium Frequency
> >> Standard Primer" of William J. Riley which has a lot of info in it
> >> covering a lot of the things that goes into it. This includes a lot of
> >> photo of the actual inner parts of the rubidium clocks. There is more
> >> material to gather, but already that book will answer a lot of things
> >> for you and summarizes a lot of stuff in a very condensed and straight
> >> forward way.
> >>
> >> Cheers,
> >> Magnus
> >>
> >> On 2023-06-08 00:38, Leo Ahluwalia via time-nuts wrote:
> >>> I appreciate all of the help so far, and assuming the procurement of a
> >>> rubidium vapour cell and rubidium lamp (and of course all the other
> >>> components), I was wondering how exactly the optical pumping setup
> should
> >>> be achieved (to make sure all the components are "hooked up" so to
> >> speak),
> >>> and whether there was already a standard way of achieving it along with
> >> the
> >>> installation of the magnetic shielding?
> >>>
> >>> - Leo
> >>>
> >>> On Wed, Jun 7, 2023 at 6:27 PM Bruce Griffiths via time-nuts <
> >>> time-nuts at lists.febo.com> wrote:
> >>>
> >>>> That just leaves the Rubidium lamp.
> >>>> An ECDL (external cavity diode laser) locked to the appropriate
> Rubidium
> >>>> transition is much easier to build. There are several ECDL designs in
> >> the
> >>>> literature. Mostly these are Littrow designs. A Cateye resonator
> design
> >> is
> >>>> another option. All the components required are readily availble.
> >>>> VCSEL's should be avoided as those without polarisation mode
> >> stabilisation
> >>>> gratings on the output face randomly mode hop between a pair or
> >>>> orthogonally polarised modes.
> >>>> A well designed but relatively simple ECDL can have a much narrower
> line
> >>>> width than a typical DFB laser.
> >>>>
> >>>> Bruce
> >>>>> On 08/06/2023 06:37 NZST djl via time-nuts <time-nuts at lists.febo.com
> >
> >>>> wrote:
> >>>>> The Rb capsules are available on ebay, eg:  124012486501
> >>>>> the classblowing part is done?
> >>>>>
> >>>>> On 2023-06-07 07:50, Richard (Rick) Karlquist via time-nuts wrote:
> >>>>>> On 6/7/2023 5:03 AM, Stephen C. Menasian via time-nuts wrote:
> >>>>>>
> >>>>>>> 1) some pure Rb87
> >>>>>>> 2) a glass blowing setup (and some skill)
> >>>>>>> 3) A selection of inert gasses (at least including Ar)
> >>>>>>> 4) Light source (Rb discharge was used then with a circular
> >> polarizer;
> >>>>>> At HP we had really skilled glass blowers, with specific experience
> in
> >>>>>> making Rb glassware.  We had to use an exotic grade of glass that
> was
> >>>>>> only one step removed from fused quartz.  It had a part number that
> I
> >>>>>> don't remember.  Very difficult to work with.
> >>>>>>
> >>>>>> The Rb lamp (one of three pieces of glassware) is very tricky to
> work
> >>>>>> with.  We used a resonant coil driven at 95 MHz at several watts.
> >>>>>> The trick is to "strike" the plasma and make the lamp light up;
> >>>>>> you can at least see visible light when that happens. I spent a
> >>>>>> lot of time fooling with it.  We never got it to work as
> >>>>>> well as the 5065 lamp.
> >>>>>>
> >>>>>> BTW, one of the Rb isotopes is slightly radioactive.  Might be
> >>>>>> hard to get as a hobbyist due to regulations.  The physicist I
> >>>>>> sat next to had a tank of it illegally stored in his cubicle.
> >>>>>>
> >>>>>> Rick
> >>>>>> N6RK
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