[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

[Lux, Jim]

On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts 
> <time-nuts at lists.febo.com> wrote:
>
>     On the subject of rapid warm up. I suppose if you had a need, one
>     could
>     dump as much power as you need into the heater. Turn on oscillator,
>     lights in room dim for a few moments.
>
>
> Is that not likely to damage a crystal? Different parts of the crystal 
> and likely to be at significantly different temperatures at the same 
> time, putting a lot of stress on the crystal due to a thermal 
> gradient. It's probably a bit academic, as nobody is going to make an 
> oven that heats up in fractions of a second, but if one did, I suspect 
> it might not do the crystal a lot of good. This is only an educated 
> guess - I don't have anything to back it up.
Oh, it would be disastrous, although quartz is pretty strong, all the 
rest of the mounting components might not be.
>
> At the other extreme,  would there be any advantage in actually 
> heating the crystal very slowly, over the course of an hour/day/week, 
> so the temperature gradient across the crystal is very small? Of 
> course, if an oven took ages to reach the correct temperature, it 
> would be inconvenient for most applications, but for some 
> applications, the advantages might outweigh the disadvantages. Of 
> course, if one does this, I suspect one would have to cool the crystal 
> slowly too to prevent a significant thermal gradient across the crystal.
>
> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. 
> I was told that Nikon cools the front element over a period of 6 
> months to reduce stresses in the glass.

Big glass mirrors for telescopes do the same.



>
> Dave