[time-nuts] hm H Maser
kb8tq at n1k.org
Wed Jan 11 07:22:38 EST 2017
A spherical set of cells is going to be a massive pain to fabricate. I believe you can hit < 5x10^-12 / sqrt(tau) with
a fairly normal cell design and cavity design. There are some very basic issues with the photo detector’s S/N that
also tip things towards a coaxial approach.
> On Jan 10, 2017, at 10:43 PM, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> A spherical cavity resonator with a spherical Rubidium cell configured as an integrating sphere (to enhance the SNR of the optical absorption signal) is a potential option. Its also possible to use the same cell to lock a 795 nm laser to the desired wavelength. Fiber coupling the laser light could also be useful.Note that with an integrating sphere (or any other random scattering process eg scattering from colloidal particles undergoing Brownian motion) laser polarisation isn't preserved which may be convenient.One potential issue with an integrating sphere is the longevity of the diffusing coating (typically Barium sulphate with an organic binder). Roughening (fine grind followed by HF etch for stress relief) the outer surface of the cell is also advisable to eliminate light pipe effects in the cell wall.
> On Wednesday, 11 January 2017 3:54 PM, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> A goal with ADEV ~ 1E-13/Tau (for Tau <1000sec) may be feasible as its already been done as part of a PhD thesis.Using as large a cavity as possible is probably useful so that a large cell can be employed.What resonant mode is desirable in the cavity?Do we need to avoid field reversal as in the hydrogen maser?
> On Wednesday, 11 January 2017 3:43 PM, Bob Camp <kb8tq at n1k.org> wrote:
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