[time-nuts] Voltage standards

[Lux, James P]

On 11/30/08 4:27 PM, "M. Warner Losh" <imp at bsdimp.com> wrote:

> The thing that got me was the word 'really' in Bruce's statement.  It
> read like someone who had tried it, had limited success, but in the
> end wound up believing that while possible, it wasn't really
> practical.  After thinking that, I couldn't imagine that somebody on
> the list hadn't tried it for some reason or another over the years.
>
> After all, as you say, a fine bottle of scotch isn't that expensive
> when it comes to the pursuit of your obsessions :)
>
> Warner

And surely, with these grim economic times, liquid helium dewars are going
to be popping up on the surplus market. Then, at least, you'll have a place
to store that liquid helium.

And speaking of cryogens, has anyone on the list done cryogenic sapphire
ring oscillators? (at home)  After all, folks at JPL are doing this
" We present design progress and subsystem test results for a new short-term
frequency standard, the Voltage Controlled Sapphire Oscillator (VCSO).
Included are sapphire resonator and coupling design, cryocooler
environmental sensitivity tests, Q measurement results, and turnover
temperature results. A previous report presented history of the design
related to resonator frequency and frequency compensation [1]. Performance
goals are a frequency stability of 1×10-14 (1 second ≦ τ ≦100 seconds) and
two years or more continuous operation. Long-term operation and small size
are facilitated by use of a small Stirling cryo-cooler (160W wall power)
with an expected 5 year life." http://hdl.handle.net/2014/39769

Seems that running a cryocooler is probably a bit easier than pouring liters
of liquid helium into a cryostat.


Jim