Hi On Jun 30, 2013, at 2:44 PM, Magnus Danielson <[email protected]> wrote:
> Hi Bob, > > On 06/30/2013 06:30 PM, Bob Camp wrote: >> Hi >> >> Ummm…. errrr…. not so much. >> >> Ions in the lattice are part of the crystal structure. When you "move" them >> by sweeping you put stress on the quartz. That stress may take a *long* time >> to relax out. Since there is now a defect in the lattice (where the ion was) >> the stress may be relieved by an ion moving back to that location. >> >> Quartz is swept to reduce it's radiation sensitivity. That's a big deal if >> you are going to put the oscillator in outer space or if you expect to need >> to use it when unexpected bright lights appear in the sky. Neither one is >> likely to be of interest in a typical basement lab. The levels involved also >> would drive you to radiation harden the rest of the oscillator circuit, not >> just the crystal. >> >> There have been a series of papers on various influences on crystals. If the >> blank is an SC, it can be tuned by an applied DC voltage. Many precision >> parts have a DC short across the resonator for this reason. In that case, >> you would not see anything to drive an ion anyway. > > NIST have been using this effect for precision phase modulations. > > I don't agree that swept crystal has not been talked about. It is mentioned > all over the precision crystal papers, it's there if you look for it. It > however does not make much sense to discuss it for us, since we usually deal > with complete oscillators and only rarely work with single crystals, and in > that case very rarely of the quality where swept crystals occurs. > > There is definitely more to it than sweeping the crystal. > > Thanks Bob for the extra insight. The way sweeping works, won't a number of > additional runs help to re-melt the crystal and help "ironing out" the > dislocations in the crystal? That's not the way it's done. One pass under bias, pull the ions to the edges. Cut off the edges. If you re-melt and re-grow the crystal you get a whole new batch of ions from the growing process. Bob > > Cheers, > Magnus > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
