Scientific Publications

[Tetrahedrite]

Just a thought inspired by a thread asking how scientific journals work:

 

Although there are many amatuer scientists who frequent this site, there are also quite a number of researchers, university graduates/postgraduates and professionals who are members here (myself included). These people may have a number of scientific publications, journal articles, research interests etc that are of interest to the various areas in the forum.

 

I was thinking that if some of these people were to post some of their research articles (links) or simply tell others about what their research involves and why it is important, it may be a way of promoting real applied science to those amatuers as a university or career option. I know many of the members here are high school students, and I think that something like this would be a benefit to the members as well as promoting science forums as a credible arena for science discussion.

 

What does everyone else think? Just a thought anyways........

[swansont]

Here you go (all atomic clock related)

 

another (pdf) and yet another (pdf) (these are magneto-optic trapping/slow atomic beam papers)

[Douglas]

(all atomic clock related)

I read one of the cesium clock articles, trying to glean some phase noise info from it.

 

We used to use rubidium clocks in some of the surveillance electronics developed for the navy. Low phase noise was our prime concern. We often wondered how a rubidium compared with a cesium in terms of phase noise, which reflects stability.

[swansont]

I read one of the cesium clock articles' date=' trying to glean some phase noise info from it.

 

We used to use rubidium clocks in some of the surveillance electronics developed for the navy. Low phase noise was our prime concern. We often wondered how a rubidium compared with a cesium in terms of phase noise, which reflects stability.[/quote']

 

Depends on the crystal and how far from carrier you are measuring. We reference our fountains to quartz crystals because of phase-noise characteristics close to carrier (5 MHz signal, ~ -140 dBc 1 Hz from carrier). We lock that to a hydrogen maser with a phase-lock-loop that has a several second time constant.

 

Taking a rubidium standard at random, the Symmetricom 8040C lists the phase noise on the 10 MHz output to be -100 dBc at 1 Hz from carrier. The datasheet for the HP 4071A shows its phase noise to also be -100 dBc. But we are a little strange in wanting good specs that close to carrier.

[Douglas]

Depends on the crystal and how far from carrier you are measuring. We reference our fountains to quartz crystals because of phase-noise characteristics close to carrier (5 MHz signal' date=' ~ -140 dBc 1 Hz from carrier). We lock that to a hydrogen maser with a phase-lock-loop that has a several second time constant.

 

Taking a rubidium standard at random, the Symmetricom 8040C lists the phase noise on the 10 MHz output to be -100 dBc at 1 Hz from carrier. The datasheet for the HP 4071A shows its phase noise to also be -100 dBc. But we are a little strange in wanting good specs that close to carrier.[/quote']

Interesting, I'm assuming that you're measuring the phase noise in a 1 Hz bandwidth, at 1 Hz from the carrier. Since your measurments are in dBc, do you happen to know the output level of the devices in dBm?? And why on earth would you be interested in phase noise that close to the carrier???

 

For our applications, we'd be interested in the phase noise level at about 1Khz from the carrier, this is so we don't convert our own L.O. phase noise into our bandwidth due to a large adjacent signal.

 

Interesting also, about the very narrow loop bandwidth, which I understand, since you don't want the maser noise transferred to the signal under measurment.

 

BTW, do you happen to know the phase noise level of these clean sources at say.....10Khz from the carrier, I'd be interested to know how close they get to Ktb @ -174 dBm.

[Douglas]

(5 MHz signal, ~ -140 dBc 1 Hz from carrier). .

I got a chuckle out of the -140 dBc, This was a topic of conversation, the minus sign is used by many people, however, since dBc means relative to the carrier, some say the minus sign should be stripped off.

[Tetrahedrite]

Interesting research, does the US Navy have units specifically aimed at specific areas of R&D? Do you have to get security clearances to publish any of your work, no matter what the subject?

[ydoaPs]

i'll ask my recruiter to find out about that.

[Mokele]

While I don't have anything out at the moment, that's definitely going to change soon (and my prof is leaning on me *hard* to make sure that's the case). When I do publish, I'll be sure to post links here. It's basically all going to be about snake locomotion.

 

Mokele

[swansont]

Interesting research, does the US Navy have units specifically aimed at specific areas of R&D? Do you have to get security clearances to publish any of your work, no matter what the subject?

 

Well, in addition to the Naval Observatory there's the Naval Research Lab, and the Office of Naval Research, which directs (and funnels money to) relevant research projects, so...yes.

 

 

The stuff I do is unclassified. I imagine that some other research is classified and to publish it has to be sanitized, and some of it just isn't published at all.

[swansont]

BTW, do you happen to know the phase noise level of these clean sources at say.....10Khz from the carrier, I'd be interested to know how close they get to Ktb @ -174 dBm.

 

The spec sheets are readily available online. These are commercial products - they want you look at (and buy) them. IIRC Symmetricom just bought the HP timing division, so all of it may be at Symmetricom's website.

[swansont]

And why on earth would you be interested in phase noise that close to the carrier???

 

 

It's the nature of the measurement. We sample the signal about once a second, so the higher frequency noise tends to average out.

[Klaynos]

I had to give a talk on fountain atomic clocks the other day, only had 1 day to prepare and no computer *sigh*

 

Intersting stuff swansont.

 

And great idea for a thread

[swansont]

I had to give a talk on fountain atomic clocks the other day' date=' only had 1 day to prepare and no computer *sigh*

[/quote']

 

I have to know the context of this. Who would want someone to give a talk on such a narrow field with ony one day of prep?