[time-nuts] Better quartz crystals with single isotope ?

Bob kb8tq kb8tq at n1k.org
Mon Apr 23 09:49:36 EDT 2018


Hi



> On Apr 23, 2018, at 12:21 AM, Bill Hawkins <bill.iaxs at pobox.com> wrote:
> 
> Good questions.
> 
> The one that bothers me is the magnetic levitation required to compare
> the standard to anything. You can't put other materials inside the
> vacuum bell with the standard. I looked up the paper, but it's behind a
> $40 pay-wall.
> 
> Electromagnets will levitate permanent magnets, but the effect is not
> stable, with the free magnet sliding out of the field. 
> Diamagnetic materials will be stable, but the effect is so weak it would
> require superconducting electromagnets. Quartz, as it happens, is
> diamagnetic.
> 
> Now the problem is to apply identical levitation to dissimilar
> materials. This would seem to require identical superconducting magnets
> and identical levitated platforms. Identical currents can flow in the
> levitating magnets simply by connecting them in series. In order for the
> platforms to be identically levitated, they have to be an identical
> distance from the levitating magnet. Measuring that to the required
> precision could be a challenge.
> 
> Machining physical parts can be done to 10 E-6. That's not enough, so
> the mechanism will require calibration. I suppose they could compare it
> to the present platinum standard. Then there's the question of
> calibration interval, and what to use as the standard. Counting
> oscillations of atoms would be so much easier.
> 
> I think Rick's three points make this a non-starter. It's a case of
> experts in metrology not having enough expertise in quarts resonators.

Just for the record John Vig knows quite a bit about quartz resonators ….

Bob


> 
> In answer to why they can't use 10 grams, the comparison has to be 100
> times more accurate than that for 1000 grams.
> 
> Hope I haven't strayed too far off topic, and wasted my time.
> 
> Bill Hawkins
> 
> 
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Richard
> (Rick) Karlquist
> Sent: Sunday, April 22, 2018 4:11 PM
> To: Discussion of precise time and frequency measurement; Bob kb8tq
> Subject: Re: [time-nuts] Better quartz crystals with single isotope ?
> 
> On 4/22/2018 10:20 AM, Bob kb8tq wrote:
> 
>>> Do we know anybody in the quartz business who needs a really cool 
>>> research project ?
>> 
>> You could put it on the list with the 1 Kg quartz resonator proposal
> ...
>> 
>> https://tf.nist.gov/general/pdf/2638.pdf 
>> <https://tf.nist.gov/general/pdf/2638.pdf>
>> 
>> Also an offshoot of people thinking about the implications of all this
> as it relates to resonators.
>> 
>> 
>> Bob
>> 
> 
> The cited article "must be true" because of its authors, I guess, but it
> makes no sense to me.  They seem to be assuming that the resonant
> frequency is inversely proportional to mass?  We all know three things:
> 
> 1.  Frequency is inversely proportional to thickness.  Not mass.
> 
> 2.  Frequency aging is affected by stress relaxation in well built
> resonators.  The old idea that mass is gradually evaporating from the
> resonator to the enclosure (glass enclosures) or mass is gradually
> evaporating from the enclosure (metal enclosures) to depositing on the
> resonator is simply obsolete in terms of current technology.
> Thus again frequency is not a proxy for mass.
> 
> 3. Resonators can "jump" in frequency without jumping in mass.
> 
> Given these facts, I am lost as how this is supposed to work.
> Surely, the authors are well aware of the 3 items above.
> 
> Also, why does the resonator have to be a whole kilogram anyway.
> If it weighed exactly 10 grams, couldn't you still compare it to a
> kilogram using 100:1 leverage?
> 
> Can anyone straighten me out?
> 
> Rick
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