Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Ole Petter Rønningen]

Hi, Dana.

> What does 'EFOS' mean?  I hadn't heard the term before.

EFOS was a series of masers made by Oscilloquartz in Switzerland, there is a 
little information on my website www.efos3.com under «about».

The manuals for those masers are also available, lots of good info for the 
interested: 
http://www.leapsecond.com/museum/efos/

> I do hear mixed reports about where the conversion to atomic H
> occurs, and consider the jury to still be out on that question.

Well, I think that jury is in.. :) plenty of information in old papers on that 
part.

Ole

> I had thought that the volume of the storage bulb was much
> smaller in out maser, perhaps in the pint to quart range.  For a
> frequency of ~1420 MHz, I guess it would take a cavity that is
> operating in a somewhat higher than fundamental mode if the
> volume is in the gallon regime as you suggest.  But with the
> narrow gain profile width of this transition, I supposed there'd
> be no risk of the thing running in the wrong mode.
> 
> Dana
> 
> 
> On Tue, Nov 21, 2017 at 8:14 AM, Ole Petter Ronningen > wrote:
> 
>>> On Tue, Nov 21, 2017 at 2:50 PM, Attila Kinali  wrote:
>>> 
>>> [...] The advantage of the platinum valve
>>> system is that it "generates" single atom Hydrogen, as required
>>> by the maser.
>> 
>> 
>> Picking nits here.. It was my understanding that the splitting of molecular
>> hydrogen into atomic hydrogen happens using RF in the dissociator - not in
>> the platinum leak valve. Is my understanding incorrect?
>> 
>> 
>>> Within the cavity there is a small glass bulb that keeps the atoms
>>> in the right position of the cavity field.
>> 
>> 
>> 4.5 liters in EFOS type masers - so not *that* small. I believe other
>> masers are the same order of magnitude.
>> 
>> 
>>> Yes, IIRC normal numbers are several 10s to 100s of wall collisions
>>> before the atom loses its state due to wall colisions and without
>>> contributing to the signal.
>>> 
>> 
>> Lifetime ~1 second I think
>> 
>> 
 I've long wondered what causes the slow frequency drift, typically
>>> amounting
 to about 3E-14 over a time span of several months.
>>> 
>>> Mostly changes in the wall coating leading to a different wall collision
>>> shift and mechanical changes of the cavity dimension (think air pressure
>>> and creep) leading to a different cavity pulling. To a lesser extend
>>> it's the changes in the quality of the vacuum and number of Hydrogen
>> atoms
>>> in the cavity.
>> 
>> 
>> Also aging of electronic components - coarse tuning of the cavity is done
>> by temperature, and any drift if the temperature-sensor/amplifiers etc will
>> result in drift. At least for EFOS type masers.
>> 
>> Ole
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>> 
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Bert Kehren via time-nuts]

Corby can most likely answer some of these questions, since he also has a  
maser and does maintain it. He is right now most likely still asleep, 
California  time.
Bert Kehren
 
 
In a message dated 11/21/2017 9:25:30 A.M. Eastern Standard Time,  
att...@kinali.ch writes:

On Tue,  21 Nov 2017 15:14:59 +0100
Ole Petter Ronningen   wrote:

> > [...] The advantage of  the platinum valve
> > system is that it "generates" single atom  Hydrogen, as required
> > by the maser.
> 
> Picking nits  here.. It was my understanding that the splitting of 
molecular
>  hydrogen into atomic hydrogen happens using RF in the dissociator - not  
in
> the platinum leak valve. Is my understanding incorrect?

Good  question. I don't know. I've only read a dozen or so papers on
maser  construction. I have never owned or operated one. Much less
taken appart  and studied its construction.

> > Within the cavity there is a  small glass bulb that keeps the atoms
> > in the right position of  the cavity field.
> 
> 4.5 liters in EFOS type masers - so not  *that* small. I believe other
> masers are the same order of  magnitude.

Hehe.. Yes. It's "small" compared to the cavity. Depending  on the
exact cavity construction, the storage space can be as small as
a  tenth of the total cavity volume.


Attila Kinali

-- 
It is upon moral qualities that a  society is ultimately founded. All 
the prosperity and technological  sophistication in the world is of no 
use without that  foundation.
-- Miss Matheson, The Diamond Age, Neil  Stephenson
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Attila Kinali]

On Tue, 21 Nov 2017 14:50:48 +0100
Attila Kinali  wrote:

> The source for the Hydrogen atoms is usually a heated platinum
> valve (a heated plate of platinum that is thin enough that the
> Hydrogen will leak through). 

Several people pointed out that the valve is made of paladium
and not of platinum. Sorry about that. And thanks to everyone
who corrected me.


Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Dana Whitlow]

Hi Ole,

What does 'EFOS' mean?  I hadn't heard the term before.

I think I've heard the one-second lifetime figure before.

I do hear mixed reports about where the conversion to atomic H
occurs, and consider the jury to still be out on that question.

I had thought that the volume of the storage bulb was much
smaller in out maser, perhaps in the pint to quart range.  For a
frequency of ~1420 MHz, I guess it would take a cavity that is
operating in a somewhat higher than fundamental mode if the
volume is in the gallon regime as you suggest.  But with the
narrow gain profile width of this transition, I supposed there'd
be no risk of the thing running in the wrong mode.

Dana


On Tue, Nov 21, 2017 at 8:14 AM, Ole Petter Ronningen  wrote:

> On Tue, Nov 21, 2017 at 2:50 PM, Attila Kinali  wrote:
>
> > [...] The advantage of the platinum valve
> > system is that it "generates" single atom Hydrogen, as required
> > by the maser.
>
>
> Picking nits here.. It was my understanding that the splitting of molecular
> hydrogen into atomic hydrogen happens using RF in the dissociator - not in
> the platinum leak valve. Is my understanding incorrect?
>
>
> > Within the cavity there is a small glass bulb that keeps the atoms
> > in the right position of the cavity field.
>
>
> 4.5 liters in EFOS type masers - so not *that* small. I believe other
> masers are the same order of magnitude.
>
>
> > Yes, IIRC normal numbers are several 10s to 100s of wall collisions
> > before the atom loses its state due to wall colisions and without
> > contributing to the signal.
> >
>
> Lifetime ~1 second I think
>
>
> > > I've long wondered what causes the slow frequency drift, typically
> > amounting
> > > to about 3E-14 over a time span of several months.
> >
> > Mostly changes in the wall coating leading to a different wall collision
> > shift and mechanical changes of the cavity dimension (think air pressure
> > and creep) leading to a different cavity pulling. To a lesser extend
> > it's the changes in the quality of the vacuum and number of Hydrogen
> atoms
> > in the cavity.
>
>
> Also aging of electronic components - coarse tuning of the cavity is done
> by temperature, and any drift if the temperature-sensor/amplifiers etc will
> result in drift. At least for EFOS type masers.
>
> Ole
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> mailman/listinfo/time-nuts
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Attila Kinali]

On Tue, 21 Nov 2017 15:31:25 +0100
Ole Petter Ronningen  wrote:

> > Hehe.. Yes. It's "small" compared to the cavity. Depending on the
> > exact cavity construction, the storage space can be as small as
> > a tenth of the total cavity volume.
> 
> Thats interesting, I would think a small volume would result in increased
> spin exchange - do you have any papers detailing the tradeoffs with
> big/small storage bulbs?

I would have to go through my collection to find those that mention
anything on it.

The tradeoff is bascially, that you want to have an as large volume
as possible to minimize wall and atom-atom collisions. But there is
only a certain volume within the cavity, where the field has the
right orientation. The higher the mode of the cavity, the smaller
the volume (relative to the cavity size). Higher cavity modes are
used to shrink the overall cavity size, without the need of loading,
which introduces losses. 

Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Ole Petter Ronningen]

>
>
> > 4.5 liters in EFOS type masers - so not *that* small. I believe other
> > masers are the same order of magnitude.
>
> Hehe.. Yes. It's "small" compared to the cavity. Depending on the
> exact cavity construction, the storage space can be as small as
> a tenth of the total cavity volume.


Thats interesting, I would think a small volume would result in increased
spin exchange - do you have any papers detailing the tradeoffs with
big/small storage bulbs?
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Attila Kinali]

On Tue, 21 Nov 2017 15:14:59 +0100
Ole Petter Ronningen  wrote:

> > [...] The advantage of the platinum valve
> > system is that it "generates" single atom Hydrogen, as required
> > by the maser.
> 
> Picking nits here.. It was my understanding that the splitting of molecular
> hydrogen into atomic hydrogen happens using RF in the dissociator - not in
> the platinum leak valve. Is my understanding incorrect?

Good question. I don't know. I've only read a dozen or so papers on
maser construction. I have never owned or operated one. Much less
taken appart and studied its construction.

> > Within the cavity there is a small glass bulb that keeps the atoms
> > in the right position of the cavity field.
> 
> 4.5 liters in EFOS type masers - so not *that* small. I believe other
> masers are the same order of magnitude.

Hehe.. Yes. It's "small" compared to the cavity. Depending on the
exact cavity construction, the storage space can be as small as
a tenth of the total cavity volume.


Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Ole Petter Ronningen]

On Tue, Nov 21, 2017 at 2:50 PM, Attila Kinali  wrote:

> [...] The advantage of the platinum valve
> system is that it "generates" single atom Hydrogen, as required
> by the maser.


Picking nits here.. It was my understanding that the splitting of molecular
hydrogen into atomic hydrogen happens using RF in the dissociator - not in
the platinum leak valve. Is my understanding incorrect?


> Within the cavity there is a small glass bulb that keeps the atoms
> in the right position of the cavity field.


4.5 liters in EFOS type masers - so not *that* small. I believe other
masers are the same order of magnitude.


> Yes, IIRC normal numbers are several 10s to 100s of wall collisions
> before the atom loses its state due to wall colisions and without
> contributing to the signal.
>

Lifetime ~1 second I think


> > I've long wondered what causes the slow frequency drift, typically
> amounting
> > to about 3E-14 over a time span of several months.
>
> Mostly changes in the wall coating leading to a different wall collision
> shift and mechanical changes of the cavity dimension (think air pressure
> and creep) leading to a different cavity pulling. To a lesser extend
> it's the changes in the quality of the vacuum and number of Hydrogen atoms
> in the cavity.


Also aging of electronic components - coarse tuning of the cavity is done
by temperature, and any drift if the temperature-sensor/amplifiers etc will
result in drift. At least for EFOS type masers.

Ole
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[time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Attila Kinali]

On Tue, 21 Nov 2017 04:24:51 -0600
Dana Whitlow  wrote:

> This is an active maser, meaning a self-sustaining oscillator whose gain
> medium
> was a volume of hydrogen atoms (at low pressure) maintained in a population-
> inverted state by squirting a thin stream of state-selected H atoms into a
> glass bulb,

They are not maintained in this state. Rather the Hydrogen atoms are
"used up" by emiting a photon at 1.4GHz. They are then "removed"
by leaking out of the opening of the bulb and pumped away.
The source for the Hydrogen atoms is usually a heated platinum
valve (a heated plate of platinum that is thin enough that the
Hydrogen will leak through). The advantage of the platinum valve
system is that it "generates" single atom Hydrogen, as required
by the maser. These atoms go through a specially formed magnet
that deflects the atoms that are in the wrong state (c.f. Stern-Gerlach
experiment). Those in the right state make it into the cavity.
Within the cavity there is a small glass bulb that keeps the atoms
in the right position of the cavity field. In order not to perturbe
the atoms too much, the bulb walls are coated with Teflon.

> The inside of the bulb was treated so that the collisions with the surface did
> not usually cause a quantum state change of the H atom involved.  I've read 
> that
> the average excited atom typically "survived" a large number of such wall
> collisions before being "consumed" by contributing a quantum of energy to
> the oscillating mode; this has always amazed me.

Yes, IIRC normal numbers are several 10s to 100s of wall collisions
before the atom loses its state due to wall colisions and without
contributing to the signal.

> So the primary frequency-determining mechanism is the collision-broadened
> line width of the gain mechanism. However, the cavity resonance exhibits a
> noticeable frequency-pulling effect, and our maser has a feedback loop that
> strives to keep the cavity tuned to the center of the medium's gain
> profile.
> But I think this loop is not a tight loop, ergo not completely successful.

The loop is quite tight. But there are multiple effects that prevent
perfect operation. Major problems are the low signal levels and the
shifts due wall colisions and cavity pulling.

> I've long wondered what causes the slow frequency drift, typically amounting
> to about 3E-14 over a time span of several months.

Mostly changes in the wall coating leading to a different wall collision
shift and mechanical changes of the cavity dimension (think air pressure
and creep) leading to a different cavity pulling. To a lesser extend
it's the changes in the quality of the vacuum and number of Hydrogen atoms
in the cavity.


Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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