[time-nuts] Home built cesium clocks???

Magnus Danielson magnus at rubidium.dyndns.org
Sun Jun 29 08:17:55 EDT 2008


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: <7.0.1.0.1.20080629120421.01ebecc8 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.

Cheers,
Magnus



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