Hi

It’s been way too many years since my last Maser play session …

Will it fire up without the Teflon coating on the bulb? Yes it works better with the Teflon (less wall interaction). Getting the bulb re-coated might be a major pain. It does look ugly in it’s current state. I’m wondering about just stripping the bulb and then seeing what works and what does not.

Bob

On Sun, 2 Nov 2014 16:28:47 -0500
Bob Camp kb8tq@n1k.org wrote:

According to some of the papers i've read, parafin might be an alternative
to Teflon. The interaction of Hydrogen with Teflon is lower than with
Parafin, but it might be acceptable (Curiously, if it were a Rb maser,
you'd use a parafin coating instead of a Teflon coating).

			Attila Kinali

--
I pity people who can't find laughter or at least some bit of amusement in
the little doings of the day. I believe I could find something ridiculous
even in the saddest moment, if necessary. It has nothing to do with being
superficial. It's a matter of joy in life.
-- Sophie Scholl

Hi Attila,

On 11/02/2014 10:43 PM, Attila Kinali wrote:

Parafin was used early, but in the strive to even further increase the
interaction time with the hydrogen in the "bouncing box", telfon was
preferred.

In the early days they experimented with different coatings. The goal
was to increase the time (and thus narrowing the bandwidth) of
interaction before the hydrogen atoms loose state and cause a frequency
shift. Rubidium gas cells have similar wall-shift, but advancements have
stabilized the wall-shift by buffer-gas selection.

A way to estimate the wall-shift is to run different sizes of
glas-bulbs, and notice the maser frequency shift.

The old hydrogen masers where really experimental platsforms to a much
higher degree, but that also meant that validation was done.

Then again the cavity shift is there, something that can be measured and
compensated as a separate control loop, which has contributed to
increase the stability and thus performance. Some hydrogen masers have
proven themselves to be much more pressure sensitive than others.

Finding the lack of hydrogen masers in my lab disturbing.

Cheers,
Magnus

Hi

OK, it works better if it bounces off the wall. The line width is narrower. Does it work at all (is there a line you can find) without the coating?

Yes you would need to find a paper from the 1960’s to find anybody trying to run one that way.

Bob

Bob,

Yes, but your Q will suffer.

Yes, I've dug out aged papers. I was sad to see that JPLs server was
taken down before I got to download their wealth of papers. Naturally it
happen just after I found out it also had a hydrogen maser section, but
also Chuck's papers was lovely to have collected in that form.

I have been lazy not to read up on all the hydrogen maser I have in
book-form at home... should definitely read up more on those.

It is interesting to see how variation on themes got considerable
narrower somewhere in the 60/70s shift to the rubidium gas-cell, active
and passive hydrogen maser and finally cesium atomic beam. It seems like
the knowledge of why they narrowed down to that set is somewhat lost to
most, but as one reads up on the old stuff one learns of the variation
of these themes that have been tested. The CSAC thus belongs to the gas
cell type for instance, with that set of problems, but with a few twist
and turns. The fountains (Cs or Rb) is a variation of the beam
apparatus, but with a few twist and turns. The ion clocks is really an
extension of the hydrogen maser's bouncing box in it's attempt to create
long observations times.

I think I recall that someone attempted a cryogenic hydrogen maser,
which would have benefits as to the lower temperature and thus speed of
the hydrogen atoms, producing even longer observations times. Hydrogen
being so darn light get into high speed for the temperature. Oh, some
doppler benefits would also to be expected.

Cheers,
Magnus

On 11/02/2014 11:20 PM, Bob Camp wrote:

Hi

Ok, so it might / might not work depending on how high a Q it needs to start functioning. I think I might try it before I went crazy coating he bulb. There will be a lot of weird things to debug and associated tear downs to find them. Having a fragile bulb coating to deal with on top of everything else might just be more than can be dealt with.

Bob

Bob,

On 11/03/2014 12:19 AM, Bob Camp wrote:

It is worth knowing that active masers have a span for how the hydrogen
in-flux will make it oscillate or not. Too little or too high, and the
oscillation will die off. It may be one of the things to tune up if you
got an older one which needs a bit of good old Love, Tender and Care.

If you don't dare, I can pass you the appropriate address for it. ;-)

Cheers,
Magnus

On 11/2/14, 3:09 PM, Magnus Danielson wrote:

which server was that?  I know they rearranged a lot of the technical
report servers, and then there was that "we don't know if it's export
controlled, so take it off line until we figure it out" episode.

It might still be there, but at a different URL.  There's been a
significant amount of reorganization within JPL over the past couple
years.  The same people are probably in the same offices and working
with the same colleagues, but the name of the group and/or it's number
might have changed.

Along with this, there's been a general reorganization of websites to
make them more consistent, but it's a "when we have time and someone to
do it" kind of thing for most sections/groups.  If you get lucky,
there's someone in the group who gets ambitious and does it.

The clock guys are in Section 335 (which also does stuff like GPS and
measuring the Earth's rotation, and science done with GPS propagation)

A bit of googling did not find a public org chart.. there ARE org charts
for some of the other sections, but "he/she who runs the website has to
get the approvals for public release" and some sections/groups are more
enthusiastic about this than others.  The websites are not done by some
centralized organization.

And, the org charts aren't necessarily up to date (by years, in some cases)

With lower Q, you should still be able to get some usable discriminator action in passive mode.  In that scenario an external 1420 MHz pump signal is needed to maintain the stimulated-emission process while new H atoms are coming into the storage bulb.  I imagine you'll want to try that at first, in any event, just so you can observe the hardware actually doing something.  You should see some signs of frequency discrimination long before you observe self-sustaining radiation, if I understand the process right.

Once the line width is narrow enough, through a combination of the right inlet pressure, bulb coating, cavity Q, and intercession from St. Ramsey, thermal energy is enough to sustain the "chain reaction." In other words, photons from random spontaneous-emission occurrences will be retained in the cavity rather than lost, leading to coherent stimulated emission without any outside help.  But the odds of getting all of those factors right the first time don't seem good.

-- john, KE5FX
Miles Design LLC