[time-nuts] Re: 5071B - and next a 5081A?

[Magnus Danielson]

Rick,

So, optical pumping has several benefits.

First of all, rather than selection magnet A, you pump all atoms into 
the same state. This means that rather than bending half of them away 
from the rest of the beam, they progress. This doubles the beam flow, 
improving the S/N. You can then choose to change the rate of cesium to 
make it last longer or get the improved quality. The actual numbers [1] 
is that 22% is in clock transition rather than 7% of total atoms, so 
that's an 3 times larger amount.

Similarly you replace the B magnet, but that just simplifies the device.

Also, the ionization and masspectrometer is replaced. Any issues in 
ionization gets compensated, and you rather use flourescence detection.

The downside is that one has to operate the lasers such that they 
survive long-term. So you traded problems. Then again, these lasers sit 
outside of the physical package, so that is easier to manage.

None of these things is a significant step forward, but a step forward. 
You get somewhat better performance.

That's at least how I understand it. Oscilloquartz have built a 
commercial optical cesium, and it has been shipped.

[1] "Optically pumped small cesium beam standards: a status report". 
https://tf.nist.gov/general/pdf/732.pdf

Cheers,
Magnus

On 2023-06-13 20:24, Richard Karlquist via time-nuts wrote:
> Len Cutler (5071 project leader) always wanted to do an optically pumped
> Cs.  But he never could get funding from HP/Agilent.  About 5 years ago,
> at the funeral for Lou Mueller, I met a manager from Microchip (or maybe
> it was Microsemi then) who told me that lasers were still not
> sufficiently reliable to use for a Cs beam unit.  It is not clear to me
> that optical pumping would improve the accuracy/stability either.  It
> would supposedly improve the Allan deviation.  The other possible
> improvement to the 5071 would be to make a reversible CBT, like NIST
> uses in their big clocks.  This is something that seems possible to
> improve accuracy.  It would obviously be a very big redesign of the CBT,
> not to mention the electronics.  Also, I don't know if it is possible to
> simultaneously run two beams in opposite directions.  Also, keeping the
> 3U size for reversible beams is unlikely.
>
> ---
> Rick Karlquist
> N6RK
> RF Designer on the 5071A project
>
> On 2023-06-13 09:13, Tom Knox via time-nuts wrote:
>
>> I think there was a growing requirement for a ROHS 5071A, and Microchip needed to act or lose international sales. And with an instrument as widely accepted as the industry standard 5071A a major concern/fear is any radical departure could risk missing the target of the existing customer base. I think now that Microchip has a ROHS 5071B to support their base this is the time to start development of the next generation "5081A" and when complete release it alongside the 5071B. Once/If the new 5081A achieves 5071B acceptance then phase out the 5071B over the next decade.
>> My question to all of you, is if you were leading development of the next generation 5081A what design changes would you implement and what new features would you employ?
>> Perhaps we can get Microsemi to have a contest, and give a new 5081A to the winner for the best ideas. We can always dream.
>> Cheers;.
>> Tom Knox
>> SR Test and Measurement Engineer
>> Phoenix Research
>> 4870 Meredith Way Apt 102
>> Boulder, Co 80303
>> Formerly of:
>> 357 Fox Lane
>> Superior Co 80027
>> 303-554-0307
>> actast at hotmail.com
>>
>> https://www.thedenverchannel.com/news/marshall-fire/superior-man-moving-forward-after-losing-dream-research-lab-during-marshall-fire
>>
>> "Peace is not the absence of violence, but the presence of Justice" Both MLK and Albert Einstein
>> ________________________________
>> From: Tom Van Baak via time-nuts <time-nuts at lists.febo.com>
>> Sent: Tuesday, June 13, 2023 9:23 AM
>> To: time-nuts at lists.febo.com <time-nuts at lists.febo.com>
>> Cc: Tom Van Baak <tvb at LeapSecond.com>
>> Subject: [time-nuts] Re: 5071B
>>
>> I've attached a 5071B photo from the web. Quite nice looking. Same specs
>> (except now RoHS).
>>
>> They kept the yellow-green LCD, which looks more out of place now both
>> in color and tech era. Maybe OLED isn't reliable enough yet. They didn't
>> mess with the red LED display. I converted one of mine to green and
>> amber. However, the prize goes to Tom Knox for his all-blue version:
>>
>> https://febo.com/pipermail/time-nuts_lists.febo.com/2023-May/107772.html
>> https://febo.com/pipermail/time-nuts_lists.febo.com/attachments/20230513/46a02b23/attachment.jpeg
>>
>> The new black theme follows Keysight 'scopes, 3458A, and frequency
>> counters that I've seen recently. Still waiting for space gray to show
>> up in the T&F world. Does anyone know what a new 5071 costs these days?
>> I miss the era of the annual hp catalog. I'm heading to Home Depot for a
>> can of matte black spray paint to turn a parts-unit 5071A into a B.
>>
>> /tvb
>>
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