[time-nuts] WTS: Efratom PTB-100 Precision Timebase

Magnus Danielson magnus at rubidium.dyndns.org
Sat Jul 7 20:08:16 EDT 2018


Hi Dana,

On 07/08/2018 02:02 AM, Dana Whitlow wrote:
> Would't it be helpful to blow a gentle jet of cooler air on the tipoff
> region during the
> rejuvenation  procedure, to encourage condensation there?

Sure, if you manage to hold it that way.
In the XSRM case, the lamp sits in a metallic holder which you then put
a metallic lamp-extractor on, which together creates a thermal cooling
to the back-end of the lamp assembly compared to the clear glass end.
This essentially achieves the same effect.

Cheers,
Magnus

> Dana
> 
> 
> On Sat, Jul 7, 2018 at 6:37 PM, Magnus Danielson <magnus at rubidium.dyndns.org
>> wrote:
> 
>> Hi,
>>
>> On 07/08/2018 12:30 AM, Gregory Beat via time-nuts wrote:
>>> In 2008, G Molenkamp, VK3UM noted that of the 20 Efratom model FRS-C
>> units he restored, component failure due to long heat exposure caused most
>> of the failures.
>>> http://www.vk3um.com/Rubidium%20rejuvination.pdf
>>> He notes that some lamps had Rb splattered over the inside wall of the
>> glass.
>>> In these cases, the Rb material was not consolidated in the “pinch of
>> the glass lamp”.
>>> Using the “heat gun process” he was able to rejuvenate those Rb lamps.
>>
>> I later tried that method on my R&S XSRM rubidium, with good progress. I
>> have reported on that on the list way back. It took two attempts, one
>> just to realize that I needed to keep the pinch at the top, because that
>> is where the hot atoms go.
>>
>> Essentially, the thin film of rubidium will consume too much of the
>> radiation to emit any useful amount of pumping light. Heating it has the
>> rubidium go into gas and then collect somewhere cold, so it's just about
>> making sure that somewhere cold isn't the glass where it is to emit light.
>>
>> My XSRM have however other issues that I need to attend to.
>>
>> Cheers,
>> Magnus
>>
>>> w9gb
>>> ==
>>>> Time-Nuts Group,
>>>> For someone interested in working on the Rb package which I believe is
>> the
>>>> FRK series. Worked great in my lab for years and recently started being
>> real
>>>> slow to lock during power cycles and now won't lock at all. Not sure
>> what
>>>> the fair asking price would be in this condition. Maybe someone has
>>>> repair/refurb experience with the Efratom FRK.
>>>> Contact me if interested.
>>>> Don
>>>
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