[time-nuts] Home built cesium clocks???
stijena at tapko.de
Sun Jun 29 15:01:51 EDT 2008
>Date: Sun, 29 Jun 2008 14:49:13 +0200
>To: Magnus Danielson <magnus at rubidium.dyndns.org>
>From: Predrag Dukic <stijena at tapko.de>
>Subject: Re: [time-nuts] Home built cesium clocks???
>One of the requirements for applying for a reference laboratory in
>Croatia is also to show "scientific excellence" in the area of work
>(of the lab).
>So I'd have to make a some original contribution to the subject and
>of course to publish it.
>It is true that at the moment I need only 250+ optical shift. That
>with 9+ GHz achieved through "optical frequency shift
>multiplication" (apart from "optical frequency multiplication" which
>is more difficult)
>is one of the ideas that I didn't find reference to in existing
>published articles. Something to be explored in the future (see
>above), but very interesting, because I could avoid phase noise from
>Another idea to be tried is to use PREDICTABLE jitter from FPGA DDS
>as phase modulation normally used to find the center of the central
>DDS achieve desired frequency by slipping reference frequency cycles
>from time to time and that way shifting the phase of the output
>signal. It is a jitter, but it is not random. Well thought
>phase shift/modulation plan can exploit this as phase modulation.
>At 14:17 29.6.2008, you wrote:
>>From: Predrag Dukic <stijena at tapko.de>
>>Subject: Re: [time-nuts] Home built cesium clocks???
>>Date: Sun, 29 Jun 2008 12:10:46 +0200
>>Message-ID: <22.214.171.124.1.20080629120421.01ebecc8 at tapko.de>
>> > Bruce,
>> > I did my homework and collected everything from the internet I could
>> > get. I have this one too.
>> > If I go optical way, I still need 9+GHz electrical source, so I will
>> > first recreate electronics. Using off the shelf DDS chips, or using FPGA.
>>A YIG oscillator or similar should be considered. The FPGA would be great
>>for the state handling, but be sure to externally reclock the signal
>>before use to remove the FPGA jitter.
>> > Also I need 9 GHz AOM, so that I can split the same optical beam and
>> > have two wavelengths 9ghz apart. That is a problem because I have
>> > only 350 MHz AOM.
>>In the article he referenced, the AOM only needs to handle 250,1 MHz.
>>Only if you intend to achieve 100% pumping and detection ratios you need
>>a full set of frequencies. Notice the important note on relation between
>>laser linewidth and S/N relationship. Luckilly those are limitations
>>outside of the cavity.
>>The interesting aspect with an optically pumped cesium is that one of the
>>common failuremodes, the contamination of the masspectrometer is removed.
>>The detection is off-axis from the beam. Wonder if an open oven could not
>>be installed there. That would allow for a ping-pong mode of operation,
>>which the optical pumping itself fits very nicely too. It would cancel
>>some of the systematic shifts due to assymetries in the microwave
>>assembly which to the best of my knowledge is hard to compensate normally.
>>Maybe state of art designs have found a way to handle it properly.
>> > Multiple pass is difficult, it would take cca 27 passes to get 9
>> > GHz. On the other side, I wouldn't need the last stages of SRD
>> > multiplication to get 9 GHz microwave.
>> > No doubt, I will have a lot of fun with the project.
>>Surely. It could be hairpulling too.
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