Poul-Henning,
On 11/05/2016 12:04 AM, Poul-Henning Kamp wrote:
--------
In message <59dc074a-3a09-6315-29d4-6877c3bf7...@rubidium.dyndns.org>, Magnus
Danielson write
s:
With respect to precision machining, that space has changed a lot
over the last five years, with precision CNC machines, factory
or home-built, dropping dramatically in price.
You need to tune it regardless.
First: Yes, but if you pick a sensible vibration mode for your
microwave resonance, that can be done with an screw-in endcap.
Indeed.
Second: No, I would actually not need to tune it.
Historically resonance cavities were used so that step/avalance
diode multipliers had enough power to excite them. Today we have
semiconductors which work at those frequencies.
Later people kept the resonance, because it works well with low
power budgets in telecoms/milspec applications.
But the resonanance leads to all sorts of trouble, including frequency
pulling, temperature sensitivities etc.
We're neither space nor power constrained, we'd probably be
perfectly happy if the end result is 4U and 100W, so resonance
is not mandatory.
Sure, but if you do have a cavity, as you was hinting at, tuning it is
still needed for the cavity pull effect.
Third: A lot of the "everybody knows" about which atoms can be
used for active vs. passive atomic standards comes from the
state of the art electronics about 30 years ago.
Sure, but some behaviors just remains there when still using such setups.
Using laser-pumping and modern semiconductors, it might actually
be possible to detect the 6.8GHz photons from the Rb.
They won't be coherent photons, like in a Hydrogen maser, but we
don't need them to be, in fact that just causes the same exact
problems as the tuned cavity anyway, as long as we can measure
the frequency well enough.
You can avoid the cavity using sidebands of the pumping laser and all
that, yes I know.
Active maser like the hydrogen would be possible naturally, but would
require the resonator.
A passive direct observation would also possible, but detection will be
harder and then you would run into S/N issues.
(No, I havn't done the math on this, my wife has banned me from
starting any new projects until our house is finished.)
Probably a wise thing.
Cheers,
Magnus
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