LJ
Lux, Jim
Fri, Jun 10, 2022 10:38 PM
On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts
time-nuts@lists.febo.com wrote:
On the subject of rapid warm up. I suppose if you had a need, one
could
dump as much power as you need into the heater. Turn on oscillator,
lights in room dim for a few moments.
Is that not likely to damage a crystal? Different parts of the crystal
and likely to be at significantly different temperatures at the same
time, putting a lot of stress on the crystal due to a thermal
gradient. It's probably a bit academic, as nobody is going to make an
oven that heats up in fractions of a second, but if one did, I suspect
it might not do the crystal a lot of good. This is only an educated
guess - I don't have anything to back it up.
Oh, it would be disastrous, although quartz is pretty strong, all the
rest of the mounting components might not be.
At the other extreme, would there be any advantage in actually
heating the crystal very slowly, over the course of an hour/day/week,
so the temperature gradient across the crystal is very small? Of
course, if an oven took ages to reach the correct temperature, it
would be inconvenient for most applications, but for some
applications, the advantages might outweigh the disadvantages. Of
course, if one does this, I suspect one would have to cool the crystal
slowly too to prevent a significant thermal gradient across the crystal.
I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
I was told that Nikon cools the front element over a period of 6
months to reduce stresses in the glass.
Big glass mirrors for telescopes do the same.
On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts
> <time-nuts@lists.febo.com> wrote:
>
> On the subject of rapid warm up. I suppose if you had a need, one
> could
> dump as much power as you need into the heater. Turn on oscillator,
> lights in room dim for a few moments.
>
>
> Is that not likely to damage a crystal? Different parts of the crystal
> and likely to be at significantly different temperatures at the same
> time, putting a lot of stress on the crystal due to a thermal
> gradient. It's probably a bit academic, as nobody is going to make an
> oven that heats up in fractions of a second, but if one did, I suspect
> it might not do the crystal a lot of good. This is only an educated
> guess - I don't have anything to back it up.
Oh, it would be disastrous, although quartz is pretty strong, all the
rest of the mounting components might not be.
>
> At the other extreme, would there be any advantage in actually
> heating the crystal very slowly, over the course of an hour/day/week,
> so the temperature gradient across the crystal is very small? Of
> course, if an oven took ages to reach the correct temperature, it
> would be inconvenient for most applications, but for some
> applications, the advantages might outweigh the disadvantages. Of
> course, if one does this, I suspect one would have to cool the crystal
> slowly too to prevent a significant thermal gradient across the crystal.
>
> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
> I was told that Nikon cools the front element over a period of 6
> months to reduce stresses in the glass.
Big glass mirrors for telescopes do the same.
>
> Dave
BG
Bruce Griffiths
Sat, Jun 11, 2022 1:11 AM
Its far more likely that the glass blank from which the front element is machined is annealed over six months rather than the element itself as precision optical element fabrication doesn't add strain to the element. Some low dispersion glasses have relatively high TCE and are very sensitive to thermal shock. Elements made from such glasses are rarely used as front elements particularly in larger sizes to avoid element fracture due to thermal shock.
Bruce
On 11/06/2022 10:38 Lux, Jim via time-nuts time-nuts@lists.febo.com wrote:
On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts
time-nuts@lists.febo.com wrote:
On the subject of rapid warm up. I suppose if you had a need, one
could
dump as much power as you need into the heater. Turn on oscillator,
lights in room dim for a few moments.
Is that not likely to damage a crystal? Different parts of the crystal
and likely to be at significantly different temperatures at the same
time, putting a lot of stress on the crystal due to a thermal
gradient. It's probably a bit academic, as nobody is going to make an
oven that heats up in fractions of a second, but if one did, I suspect
it might not do the crystal a lot of good. This is only an educated
guess - I don't have anything to back it up.
Oh, it would be disastrous, although quartz is pretty strong, all the
rest of the mounting components might not be.
At the other extreme, would there be any advantage in actually
heating the crystal very slowly, over the course of an hour/day/week,
so the temperature gradient across the crystal is very small? Of
course, if an oven took ages to reach the correct temperature, it
would be inconvenient for most applications, but for some
applications, the advantages might outweigh the disadvantages. Of
course, if one does this, I suspect one would have to cool the crystal
slowly too to prevent a significant thermal gradient across the crystal.
I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
I was told that Nikon cools the front element over a period of 6
months to reduce stresses in the glass.
Big glass mirrors for telescopes do the same.
Dave
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
Its far more likely that the glass blank from which the front element is machined is annealed over six months rather than the element itself as precision optical element fabrication doesn't add strain to the element. Some low dispersion glasses have relatively high TCE and are very sensitive to thermal shock. Elements made from such glasses are rarely used as front elements particularly in larger sizes to avoid element fracture due to thermal shock.
Bruce
> On 11/06/2022 10:38 Lux, Jim via time-nuts <time-nuts@lists.febo.com> wrote:
>
>
> On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
> > On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts
> > <time-nuts@lists.febo.com> wrote:
> >
> > On the subject of rapid warm up. I suppose if you had a need, one
> > could
> > dump as much power as you need into the heater. Turn on oscillator,
> > lights in room dim for a few moments.
> >
> >
> > Is that not likely to damage a crystal? Different parts of the crystal
> > and likely to be at significantly different temperatures at the same
> > time, putting a lot of stress on the crystal due to a thermal
> > gradient. It's probably a bit academic, as nobody is going to make an
> > oven that heats up in fractions of a second, but if one did, I suspect
> > it might not do the crystal a lot of good. This is only an educated
> > guess - I don't have anything to back it up.
> Oh, it would be disastrous, although quartz is pretty strong, all the
> rest of the mounting components might not be.
> >
> > At the other extreme, would there be any advantage in actually
> > heating the crystal very slowly, over the course of an hour/day/week,
> > so the temperature gradient across the crystal is very small? Of
> > course, if an oven took ages to reach the correct temperature, it
> > would be inconvenient for most applications, but for some
> > applications, the advantages might outweigh the disadvantages. Of
> > course, if one does this, I suspect one would have to cool the crystal
> > slowly too to prevent a significant thermal gradient across the crystal.
> >
> > I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
> > I was told that Nikon cools the front element over a period of 6
> > months to reduce stresses in the glass.
>
> Big glass mirrors for telescopes do the same.
>
>
>
> >
> > Dave
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
BK
Bob kb8tq
Sat, Jun 11, 2022 1:29 AM
On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts time-nuts@lists.febo.com wrote:
On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts time-nuts@lists.febo.com wrote:
On the subject of rapid warm up. I suppose if you had a need, one
could
dump as much power as you need into the heater. Turn on oscillator,
lights in room dim for a few moments.
Is that not likely to damage a crystal? Different parts of the crystal and likely to be at significantly different temperatures at the same time, putting a lot of stress on the crystal due to a thermal gradient. It's probably a bit academic, as nobody is going to make an oven that heats up in fractions of a second, but if one did, I suspect it might not do the crystal a lot of good. This is only an educated guess - I don't have anything to back it up.
Oh, it would be disastrous, although quartz is pretty strong, all the rest of the mounting components might not be.
Indeed, breaking a quartz blank via thermal stress would be very hard to do.
The “rest of the parts” actually are pretty durable as well. Most of it is metal and
it is quite able to handle thermal issues.
The big issue in a fast warm up AT turned out to be designing the heater and the
mount to get the energy to the blank quickly….. If you use a small enough package
and blank, the amount of power turns out to be surprisingly small.
If you want to go bonkers, you mount the heaters inside the crystal package. This
does indeed create some issues in various areas.
Bob
At the other extreme, would there be any advantage in actually heating the crystal very slowly, over the course of an hour/day/week, so the temperature gradient across the crystal is very small? Of course, if an oven took ages to reach the correct temperature, it would be inconvenient for most applications, but for some applications, the advantages might outweigh the disadvantages. Of course, if one does this, I suspect one would have to cool the crystal slowly too to prevent a significant thermal gradient across the crystal.
I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. I was told that Nikon cools the front element over a period of 6 months to reduce stresses in the glass.
Big glass mirrors for telescopes do the same.
Hi
> On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <time-nuts@lists.febo.com> wrote:
>
> On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
>> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <time-nuts@lists.febo.com> wrote:
>>
>> On the subject of rapid warm up. I suppose if you had a need, one
>> could
>> dump as much power as you need into the heater. Turn on oscillator,
>> lights in room dim for a few moments.
>>
>>
>> Is that not likely to damage a crystal? Different parts of the crystal and likely to be at significantly different temperatures at the same time, putting a lot of stress on the crystal due to a thermal gradient. It's probably a bit academic, as nobody is going to make an oven that heats up in fractions of a second, but if one did, I suspect it might not do the crystal a lot of good. This is only an educated guess - I don't have anything to back it up.
> Oh, it would be disastrous, although quartz is pretty strong, all the rest of the mounting components might not be.
Indeed, breaking a quartz blank via thermal stress would be very hard to do.
The “rest of the parts” actually are pretty durable as well. Most of it is metal and
it is quite able to handle thermal issues.
The big issue in a fast warm up AT turned out to be designing the heater and the
mount to get the energy to the blank quickly….. If you use a small enough package
and blank, the amount of power turns out to be surprisingly small.
If you want to go bonkers, you mount the heaters *inside* the crystal package. This
does indeed create some issues in various areas.
Bob
>>
>> At the other extreme, would there be any advantage in actually heating the crystal very slowly, over the course of an hour/day/week, so the temperature gradient across the crystal is very small? Of course, if an oven took ages to reach the correct temperature, it would be inconvenient for most applications, but for some applications, the advantages might outweigh the disadvantages. Of course, if one does this, I suspect one would have to cool the crystal slowly too to prevent a significant thermal gradient across the crystal.
>>
>> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. I was told that Nikon cools the front element over a period of 6 months to reduce stresses in the glass.
>
> Big glass mirrors for telescopes do the same.
>
>
>
>>
>> Dave
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
LT
Louis Taber
Sun, Jun 12, 2022 1:34 PM
I have been of the impression for years now that most "better" crystals are
in a vacuum. And the electrical and mechanical connections to the quartz
itself place as little mechanical load on the crystal as possible.
Thermal conductivity from the oven to the crystal itself would be both
hard to model and hard to speed up.
IR transmission of energy to the crystal also seems problematic considering
the IR transmission of quartz and the IR reflectivity of gold
contact plating.
Is any of this an issue?
On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <
time-nuts@lists.febo.com> wrote:
On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <
On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
On the subject of rapid warm up. I suppose if you had a need, one
could
dump as much power as you need into the heater. Turn on oscillator,
lights in room dim for a few moments.
Is that not likely to damage a crystal? Different parts of the crystal
and likely to be at significantly different temperatures at the same time,
putting a lot of stress on the crystal due to a thermal gradient. It's
probably a bit academic, as nobody is going to make an oven that heats up
in fractions of a second, but if one did, I suspect it might not do the
crystal a lot of good. This is only an educated guess - I don't have
anything to back it up.
Oh, it would be disastrous, although quartz is pretty strong, all the
rest of the mounting components might not be.
Indeed, breaking a quartz blank via thermal stress would be very hard to
do.
The “rest of the parts” actually are pretty durable as well. Most of it is
metal and
it is quite able to handle thermal issues.
The big issue in a fast warm up AT turned out to be designing the heater
and the
mount to get the energy to the blank quickly….. If you use a small enough
package
and blank, the amount of power turns out to be surprisingly small.
If you want to go bonkers, you mount the heaters inside the crystal
package. This
does indeed create some issues in various areas.
Bob
At the other extreme, would there be any advantage in actually heating
the crystal very slowly, over the course of an hour/day/week, so the
temperature gradient across the crystal is very small? Of course, if an
oven took ages to reach the correct temperature, it would be inconvenient
for most applications, but for some applications, the advantages might
outweigh the disadvantages. Of course, if one does this, I suspect one
would have to cool the crystal slowly too to prevent a significant thermal
gradient across the crystal.
I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
I was told that Nikon cools the front element over a period of 6 months to
reduce stresses in the glass.
Big glass mirrors for telescopes do the same.
I have been of the impression for years now that most "better" crystals are
in a vacuum. And the electrical and mechanical connections to the quartz
itself place as little mechanical load on the crystal as possible.
Thermal conductivity from the oven to the crystal itself would be both
hard to model and hard to speed up.
IR transmission of energy to the crystal also seems problematic considering
the IR transmission of quartz and the IR reflectivity of gold
contact plating.
Is any of this an issue?
- Louis
On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <
time-nuts@lists.febo.com> wrote:
> Hi
>
> > On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >
> > On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
> >> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >>
> >> On the subject of rapid warm up. I suppose if you had a need, one
> >> could
> >> dump as much power as you need into the heater. Turn on oscillator,
> >> lights in room dim for a few moments.
> >>
> >>
> >> Is that not likely to damage a crystal? Different parts of the crystal
> and likely to be at significantly different temperatures at the same time,
> putting a lot of stress on the crystal due to a thermal gradient. It's
> probably a bit academic, as nobody is going to make an oven that heats up
> in fractions of a second, but if one did, I suspect it might not do the
> crystal a lot of good. This is only an educated guess - I don't have
> anything to back it up.
> > Oh, it would be disastrous, although quartz is pretty strong, all the
> rest of the mounting components might not be.
>
> Indeed, breaking a quartz blank via thermal stress would be very hard to
> do.
> The “rest of the parts” actually are pretty durable as well. Most of it is
> metal and
> it is quite able to handle thermal issues.
>
> The big issue in a fast warm up AT turned out to be designing the heater
> and the
> mount to get the energy to the blank quickly….. If you use a small enough
> package
> and blank, the amount of power turns out to be surprisingly small.
>
> If you want to go bonkers, you mount the heaters *inside* the crystal
> package. This
> does indeed create some issues in various areas.
>
> Bob
>
> >>
> >> At the other extreme, would there be any advantage in actually heating
> the crystal very slowly, over the course of an hour/day/week, so the
> temperature gradient across the crystal is very small? Of course, if an
> oven took ages to reach the correct temperature, it would be inconvenient
> for most applications, but for some applications, the advantages might
> outweigh the disadvantages. Of course, if one does this, I suspect one
> would have to cool the crystal slowly too to prevent a significant thermal
> gradient across the crystal.
> >>
> >> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
> I was told that Nikon cools the front element over a period of 6 months to
> reduce stresses in the glass.
> >
> > Big glass mirrors for telescopes do the same.
> >
> >
> >
> >>
> >> Dave
> >
> > _______________________________________________
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe send an email to time-nuts-leave@lists.febo.com
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
BK
Bob kb8tq
Sun, Jun 12, 2022 4:18 PM
Hi
Well …..
The question becomes “how much of a vacuum? I surprisingly small amount
of He will have a substantial impact on heat flow. Since there will always be some
leakage / outgassing in any package design, it just might improve aging.
The days of “spring wire” mounts are long gone for precision crystals. The mounts
are short fat metal “bands” that will move heat pretty well. On the typical “TO” style
package (HC-40 etc…) the thermal path isn’t all that bad.
The location of the heaters is under the control of the OCXO designer. You can
improve the thermal path (speed wise) by moving things around. Yes, this has other
impacts that may or may not be an improvement in other areas.
Bob
On Jun 12, 2022, at 5:34 AM, Louis Taber via time-nuts time-nuts@lists.febo.com wrote:
I have been of the impression for years now that most "better" crystals are
in a vacuum. And the electrical and mechanical connections to the quartz
itself place as little mechanical load on the crystal as possible.
Thermal conductivity from the oven to the crystal itself would be both
hard to model and hard to speed up.
IR transmission of energy to the crystal also seems problematic considering
the IR transmission of quartz and the IR reflectivity of gold
contact plating.
Is any of this an issue?
On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <
time-nuts@lists.febo.com> wrote:
On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <
On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
On the subject of rapid warm up. I suppose if you had a need, one
could
dump as much power as you need into the heater. Turn on oscillator,
lights in room dim for a few moments.
Is that not likely to damage a crystal? Different parts of the crystal
and likely to be at significantly different temperatures at the same time,
putting a lot of stress on the crystal due to a thermal gradient. It's
probably a bit academic, as nobody is going to make an oven that heats up
in fractions of a second, but if one did, I suspect it might not do the
crystal a lot of good. This is only an educated guess - I don't have
anything to back it up.
Oh, it would be disastrous, although quartz is pretty strong, all the
rest of the mounting components might not be.
Indeed, breaking a quartz blank via thermal stress would be very hard to
do.
The “rest of the parts” actually are pretty durable as well. Most of it is
metal and
it is quite able to handle thermal issues.
The big issue in a fast warm up AT turned out to be designing the heater
and the
mount to get the energy to the blank quickly….. If you use a small enough
package
and blank, the amount of power turns out to be surprisingly small.
If you want to go bonkers, you mount the heaters inside the crystal
package. This
does indeed create some issues in various areas.
Bob
At the other extreme, would there be any advantage in actually heating
the crystal very slowly, over the course of an hour/day/week, so the
temperature gradient across the crystal is very small? Of course, if an
oven took ages to reach the correct temperature, it would be inconvenient
for most applications, but for some applications, the advantages might
outweigh the disadvantages. Of course, if one does this, I suspect one
would have to cool the crystal slowly too to prevent a significant thermal
gradient across the crystal.
I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
I was told that Nikon cools the front element over a period of 6 months to
reduce stresses in the glass.
Big glass mirrors for telescopes do the same.
Hi
Well …..
The question becomes “how much of a vacuum? I surprisingly small amount
of He will have a substantial impact on heat flow. Since there will always be some
leakage / outgassing in any package design, it just *might* improve aging.
The days of “spring wire” mounts are long gone for precision crystals. The mounts
are short fat metal “bands” that will move heat pretty well. On the typical “TO” style
package (HC-40 etc…) the thermal path isn’t all that bad.
The location of the heaters *is* under the control of the OCXO designer. You can
improve the thermal path (speed wise) by moving things around. Yes, this has other
impacts that may or may not be an improvement in other areas.
Bob
> On Jun 12, 2022, at 5:34 AM, Louis Taber via time-nuts <time-nuts@lists.febo.com> wrote:
>
> I have been of the impression for years now that most "better" crystals are
> in a vacuum. And the electrical and mechanical connections to the quartz
> itself place as little mechanical load on the crystal as possible.
> Thermal conductivity from the oven to the crystal itself would be both
> hard to model and hard to speed up.
>
> IR transmission of energy to the crystal also seems problematic considering
> the IR transmission of quartz and the IR reflectivity of gold
> contact plating.
>
> Is any of this an issue?
>
> - Louis
>
> On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <
> time-nuts@lists.febo.com> wrote:
>
>> Hi
>>
>>> On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <
>> time-nuts@lists.febo.com> wrote:
>>>
>>> On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
>>>> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
>> time-nuts@lists.febo.com> wrote:
>>>>
>>>> On the subject of rapid warm up. I suppose if you had a need, one
>>>> could
>>>> dump as much power as you need into the heater. Turn on oscillator,
>>>> lights in room dim for a few moments.
>>>>
>>>>
>>>> Is that not likely to damage a crystal? Different parts of the crystal
>> and likely to be at significantly different temperatures at the same time,
>> putting a lot of stress on the crystal due to a thermal gradient. It's
>> probably a bit academic, as nobody is going to make an oven that heats up
>> in fractions of a second, but if one did, I suspect it might not do the
>> crystal a lot of good. This is only an educated guess - I don't have
>> anything to back it up.
>>> Oh, it would be disastrous, although quartz is pretty strong, all the
>> rest of the mounting components might not be.
>>
>> Indeed, breaking a quartz blank via thermal stress would be very hard to
>> do.
>> The “rest of the parts” actually are pretty durable as well. Most of it is
>> metal and
>> it is quite able to handle thermal issues.
>>
>> The big issue in a fast warm up AT turned out to be designing the heater
>> and the
>> mount to get the energy to the blank quickly….. If you use a small enough
>> package
>> and blank, the amount of power turns out to be surprisingly small.
>>
>> If you want to go bonkers, you mount the heaters *inside* the crystal
>> package. This
>> does indeed create some issues in various areas.
>>
>> Bob
>>
>>>>
>>>> At the other extreme, would there be any advantage in actually heating
>> the crystal very slowly, over the course of an hour/day/week, so the
>> temperature gradient across the crystal is very small? Of course, if an
>> oven took ages to reach the correct temperature, it would be inconvenient
>> for most applications, but for some applications, the advantages might
>> outweigh the disadvantages. Of course, if one does this, I suspect one
>> would have to cool the crystal slowly too to prevent a significant thermal
>> gradient across the crystal.
>>>>
>>>> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
>> I was told that Nikon cools the front element over a period of 6 months to
>> reduce stresses in the glass.
>>>
>>> Big glass mirrors for telescopes do the same.
>>>
>>>
>>>
>>>>
>>>> Dave
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>> To unsubscribe send an email to time-nuts-leave@lists.febo.com
>> _______________________________________________
>> time-nuts mailing list -- time-nuts@lists.febo.com
>> To unsubscribe send an email to time-nuts-leave@lists.febo.com
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
RP
Ross P
Sun, Jun 12, 2022 5:18 PM
I have seen that manufacturers seal their crystals in a vacuum, maybe air interaction affects Q. The point that vacuum inhibits heat flow is something I have never considered in ovenized units. My ovenized crystals take about an hour to settle. I have some WW2 surplus crystals in non-sealed packages that I have not tested... something to do.rp
On Sunday, June 12, 2022 at 07:26:19 AM PDT, Louis Taber via time-nuts <time-nuts@lists.febo.com> wrote:
I have been of the impression for years now that most "better" crystals are
in a vacuum. And the electrical and mechanical connections to the quartz
itself place as little mechanical load on the crystal as possible.
Thermal conductivity from the oven to the crystal itself would be both
hard to model and hard to speed up.
IR transmission of energy to the crystal also seems problematic considering
the IR transmission of quartz and the IR reflectivity of gold
contact plating.
Is any of this an issue?
- Louis
On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <
time-nuts@lists.febo.com> wrote:
On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <
On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
On the subject of rapid warm up. I suppose if you had a need, one
could
dump as much power as you need into the heater. Turn on oscillator,
lights in room dim for a few moments.
Is that not likely to damage a crystal? Different parts of the crystal
and likely to be at significantly different temperatures at the same time,
putting a lot of stress on the crystal due to a thermal gradient. It's
probably a bit academic, as nobody is going to make an oven that heats up
in fractions of a second, but if one did, I suspect it might not do the
crystal a lot of good. This is only an educated guess - I don't have
anything to back it up.
Oh, it would be disastrous, although quartz is pretty strong, all the
rest of the mounting components might not be.
Indeed, breaking a quartz blank via thermal stress would be very hard to
do.
The “rest of the parts” actually are pretty durable as well. Most of it is
metal and
it is quite able to handle thermal issues.
The big issue in a fast warm up AT turned out to be designing the heater
and the
mount to get the energy to the blank quickly….. If you use a small enough
package
and blank, the amount of power turns out to be surprisingly small.
If you want to go bonkers, you mount the heaters inside the crystal
package. This
does indeed create some issues in various areas.
Bob
At the other extreme, would there be any advantage in actually heating
the crystal very slowly, over the course of an hour/day/week, so the
temperature gradient across the crystal is very small? Of course, if an
oven took ages to reach the correct temperature, it would be inconvenient
for most applications, but for some applications, the advantages might
outweigh the disadvantages. Of course, if one does this, I suspect one
would have to cool the crystal slowly too to prevent a significant thermal
gradient across the crystal.
I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
I was told that Nikon cools the front element over a period of 6 months to
reduce stresses in the glass.
Big glass mirrors for telescopes do the same.
I have seen that manufacturers seal their crystals in a vacuum, maybe air interaction affects Q. The point that vacuum inhibits heat flow is something I have never considered in ovenized units. My ovenized crystals take about an hour to settle. I have some WW2 surplus crystals in non-sealed packages that I have not tested... something to do.rp
On Sunday, June 12, 2022 at 07:26:19 AM PDT, Louis Taber via time-nuts <time-nuts@lists.febo.com> wrote:
I have been of the impression for years now that most "better" crystals are
in a vacuum. And the electrical and mechanical connections to the quartz
itself place as little mechanical load on the crystal as possible.
Thermal conductivity from the oven to the crystal itself would be both
hard to model and hard to speed up.
IR transmission of energy to the crystal also seems problematic considering
the IR transmission of quartz and the IR reflectivity of gold
contact plating.
Is any of this an issue?
- Louis
On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <
time-nuts@lists.febo.com> wrote:
> Hi
>
> > On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >
> > On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
> >> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >>
> >> On the subject of rapid warm up. I suppose if you had a need, one
> >> could
> >> dump as much power as you need into the heater. Turn on oscillator,
> >> lights in room dim for a few moments.
> >>
> >>
> >> Is that not likely to damage a crystal? Different parts of the crystal
> and likely to be at significantly different temperatures at the same time,
> putting a lot of stress on the crystal due to a thermal gradient. It's
> probably a bit academic, as nobody is going to make an oven that heats up
> in fractions of a second, but if one did, I suspect it might not do the
> crystal a lot of good. This is only an educated guess - I don't have
> anything to back it up.
> > Oh, it would be disastrous, although quartz is pretty strong, all the
> rest of the mounting components might not be.
>
> Indeed, breaking a quartz blank via thermal stress would be very hard to
> do.
> The “rest of the parts” actually are pretty durable as well. Most of it is
> metal and
> it is quite able to handle thermal issues.
>
> The big issue in a fast warm up AT turned out to be designing the heater
> and the
> mount to get the energy to the blank quickly….. If you use a small enough
> package
> and blank, the amount of power turns out to be surprisingly small.
>
> If you want to go bonkers, you mount the heaters *inside* the crystal
> package. This
> does indeed create some issues in various areas.
>
> Bob
>
> >>
> >> At the other extreme, would there be any advantage in actually heating
> the crystal very slowly, over the course of an hour/day/week, so the
> temperature gradient across the crystal is very small? Of course, if an
> oven took ages to reach the correct temperature, it would be inconvenient
> for most applications, but for some applications, the advantages might
> outweigh the disadvantages. Of course, if one does this, I suspect one
> would have to cool the crystal slowly too to prevent a significant thermal
> gradient across the crystal.
> >>
> >> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
> I was told that Nikon cools the front element over a period of 6 months to
> reduce stresses in the glass.
> >
> > Big glass mirrors for telescopes do the same.
> >
> >
> >
> >>
> >> Dave
> >
> > _______________________________________________
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe send an email to time-nuts-leave@lists.febo.com
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
_______________________________________________
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
BK
Bob kb8tq
Mon, Jun 13, 2022 1:30 AM
Hi
Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For
bonus points, open up the crystal package. If you have the gear to test it, take a look
at what the gas is inside the package. ( Good luck with that :) :) :) )
If you had the gear and the willingness to scrap out OCXO’s you would find that a number
of fast warmup OCXO’s have a tiny amount of He in the package. Measuring this would
be tough ( it’s that small). Go through the thermal modeling and it’s way more conductive
(thermal wise) than a perfect vacuum ……
Bob
On Jun 12, 2022, at 9:18 AM, Ross P via time-nuts time-nuts@lists.febo.com wrote:
I have seen that manufacturers seal their crystals in a vacuum, maybe air interaction affects Q. The point that vacuum inhibits heat flow is something I have never considered in ovenized units. My ovenized crystals take about an hour to settle. I have some WW2 surplus crystals in non-sealed packages that I have not tested... something to do.rp
On Sunday, June 12, 2022 at 07:26:19 AM PDT, Louis Taber via time-nuts <time-nuts@lists.febo.com> wrote:
I have been of the impression for years now that most "better" crystals are
in a vacuum. And the electrical and mechanical connections to the quartz
itself place as little mechanical load on the crystal as possible.
Thermal conductivity from the oven to the crystal itself would be both
hard to model and hard to speed up.
IR transmission of energy to the crystal also seems problematic considering
the IR transmission of quartz and the IR reflectivity of gold
contact plating.
Is any of this an issue?
On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <
time-nuts@lists.febo.com> wrote:
On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <
On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
On the subject of rapid warm up. I suppose if you had a need, one
could
dump as much power as you need into the heater. Turn on oscillator,
lights in room dim for a few moments.
Is that not likely to damage a crystal? Different parts of the crystal
and likely to be at significantly different temperatures at the same time,
putting a lot of stress on the crystal due to a thermal gradient. It's
probably a bit academic, as nobody is going to make an oven that heats up
in fractions of a second, but if one did, I suspect it might not do the
crystal a lot of good. This is only an educated guess - I don't have
anything to back it up.
Oh, it would be disastrous, although quartz is pretty strong, all the
rest of the mounting components might not be.
Indeed, breaking a quartz blank via thermal stress would be very hard to
do.
The “rest of the parts” actually are pretty durable as well. Most of it is
metal and
it is quite able to handle thermal issues.
The big issue in a fast warm up AT turned out to be designing the heater
and the
mount to get the energy to the blank quickly….. If you use a small enough
package
and blank, the amount of power turns out to be surprisingly small.
If you want to go bonkers, you mount the heaters inside the crystal
package. This
does indeed create some issues in various areas.
Bob
At the other extreme, would there be any advantage in actually heating
the crystal very slowly, over the course of an hour/day/week, so the
temperature gradient across the crystal is very small? Of course, if an
oven took ages to reach the correct temperature, it would be inconvenient
for most applications, but for some applications, the advantages might
outweigh the disadvantages. Of course, if one does this, I suspect one
would have to cool the crystal slowly too to prevent a significant thermal
gradient across the crystal.
I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
I was told that Nikon cools the front element over a period of 6 months to
reduce stresses in the glass.
Big glass mirrors for telescopes do the same.
Hi
Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For
bonus points, open up the crystal package. If you have the gear to test it, take a look
at what the gas *is* inside the package. ( Good luck with that :) :) :) )
If you had the gear and the willingness to scrap out OCXO’s you would find that a number
of fast warmup OCXO’s have a *tiny* amount of He in the package. Measuring this would
be tough ( it’s that small). Go through the thermal modeling and it’s *way* more conductive
(thermal wise) than a *perfect* vacuum ……
Bob
> On Jun 12, 2022, at 9:18 AM, Ross P via time-nuts <time-nuts@lists.febo.com> wrote:
>
> I have seen that manufacturers seal their crystals in a vacuum, maybe air interaction affects Q. The point that vacuum inhibits heat flow is something I have never considered in ovenized units. My ovenized crystals take about an hour to settle. I have some WW2 surplus crystals in non-sealed packages that I have not tested... something to do.rp
>
> On Sunday, June 12, 2022 at 07:26:19 AM PDT, Louis Taber via time-nuts <time-nuts@lists.febo.com> wrote:
>
> I have been of the impression for years now that most "better" crystals are
> in a vacuum. And the electrical and mechanical connections to the quartz
> itself place as little mechanical load on the crystal as possible.
> Thermal conductivity from the oven to the crystal itself would be both
> hard to model and hard to speed up.
>
> IR transmission of energy to the crystal also seems problematic considering
> the IR transmission of quartz and the IR reflectivity of gold
> contact plating.
>
> Is any of this an issue?
>
> - Louis
>
> On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <
> time-nuts@lists.febo.com> wrote:
>
>> Hi
>>
>>> On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <
>> time-nuts@lists.febo.com> wrote:
>>>
>>> On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
>>>> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
>> time-nuts@lists.febo.com> wrote:
>>>>
>>>> On the subject of rapid warm up. I suppose if you had a need, one
>>>> could
>>>> dump as much power as you need into the heater. Turn on oscillator,
>>>> lights in room dim for a few moments.
>>>>
>>>>
>>>> Is that not likely to damage a crystal? Different parts of the crystal
>> and likely to be at significantly different temperatures at the same time,
>> putting a lot of stress on the crystal due to a thermal gradient. It's
>> probably a bit academic, as nobody is going to make an oven that heats up
>> in fractions of a second, but if one did, I suspect it might not do the
>> crystal a lot of good. This is only an educated guess - I don't have
>> anything to back it up.
>>> Oh, it would be disastrous, although quartz is pretty strong, all the
>> rest of the mounting components might not be.
>>
>> Indeed, breaking a quartz blank via thermal stress would be very hard to
>> do.
>> The “rest of the parts” actually are pretty durable as well. Most of it is
>> metal and
>> it is quite able to handle thermal issues.
>>
>> The big issue in a fast warm up AT turned out to be designing the heater
>> and the
>> mount to get the energy to the blank quickly….. If you use a small enough
>> package
>> and blank, the amount of power turns out to be surprisingly small.
>>
>> If you want to go bonkers, you mount the heaters *inside* the crystal
>> package. This
>> does indeed create some issues in various areas.
>>
>> Bob
>>
>>>>
>>>> At the other extreme, would there be any advantage in actually heating
>> the crystal very slowly, over the course of an hour/day/week, so the
>> temperature gradient across the crystal is very small? Of course, if an
>> oven took ages to reach the correct temperature, it would be inconvenient
>> for most applications, but for some applications, the advantages might
>> outweigh the disadvantages. Of course, if one does this, I suspect one
>> would have to cool the crystal slowly too to prevent a significant thermal
>> gradient across the crystal.
>>>>
>>>> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
>> I was told that Nikon cools the front element over a period of 6 months to
>> reduce stresses in the glass.
>>>
>>> Big glass mirrors for telescopes do the same.
>>>
>>>
>>>
>>>>
>>>> Dave
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>> To unsubscribe send an email to time-nuts-leave@lists.febo.com
>> _______________________________________________
>> time-nuts mailing list -- time-nuts@lists.febo.com
>> To unsubscribe send an email to time-nuts-leave@lists.febo.com
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
LJ
Lux, Jim
Mon, Jun 13, 2022 3:38 AM
On 6/12/22 6:30 PM, Bob kb8tq via time-nuts wrote:
Hi
Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For
bonus points, open up the crystal package. If you have the gear to test it, take a look
at what the gas is inside the package. ( Good luck with that :) :) :) )
If you had the gear and the willingness to scrap out OCXO’s you would find that a number
of fast warmup OCXO’s have a tiny amount of He in the package. Measuring this would
be tough ( it’s that small). Go through the thermal modeling and it’s way more conductive
(thermal wise) than a perfect vacuum ……
Bob
And the worst thing is that if your vacuum sealed widget is in an
atmosphere with more He around (like waiting for a launch, in a place
that does more He leak tests, etc.), the He will diffuse into your
package and it doesn't work like expected.
On 6/12/22 6:30 PM, Bob kb8tq via time-nuts wrote:
> Hi
>
> Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For
> bonus points, open up the crystal package. If you have the gear to test it, take a look
> at what the gas *is* inside the package. ( Good luck with that :) :) :) )
>
> If you had the gear and the willingness to scrap out OCXO’s you would find that a number
> of fast warmup OCXO’s have a *tiny* amount of He in the package. Measuring this would
> be tough ( it’s that small). Go through the thermal modeling and it’s *way* more conductive
> (thermal wise) than a *perfect* vacuum ……
>
> Bob
And the worst thing is that if your vacuum sealed widget is in an
atmosphere with more He around (like waiting for a launch, in a place
that does more He leak tests, etc.), the He will diffuse into your
package and it doesn't work like expected.
BK
Bob kb8tq
Mon, Jun 13, 2022 4:28 AM
Hi
Like it or not, modern crystal packages are mad of metal ( as opposed to glass).
The gotcha with metal is that getting rid of all of the He is darn hard. That makes
a “perfect vacuum” more than a bit tough.
Bob
On Jun 12, 2022, at 7:38 PM, Lux, Jim via time-nuts time-nuts@lists.febo.com wrote:
On 6/12/22 6:30 PM, Bob kb8tq via time-nuts wrote:
Hi
Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For
bonus points, open up the crystal package. If you have the gear to test it, take a look
at what the gas is inside the package. ( Good luck with that :) :) :) )
If you had the gear and the willingness to scrap out OCXO’s you would find that a number
of fast warmup OCXO’s have a tiny amount of He in the package. Measuring this would
be tough ( it’s that small). Go through the thermal modeling and it’s way more conductive
(thermal wise) than a perfect vacuum ……
Bob
And the worst thing is that if your vacuum sealed widget is in an atmosphere with more He around (like waiting for a launch, in a place that does more He leak tests, etc.), the He will diffuse into your package and it doesn't work like expected.
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
Hi
Like it or not, modern crystal packages are mad of metal ( as opposed to glass).
The gotcha with metal is that getting rid of *all* of the He is darn hard. That makes
a “perfect vacuum” more than a bit tough.
Bob
> On Jun 12, 2022, at 7:38 PM, Lux, Jim via time-nuts <time-nuts@lists.febo.com> wrote:
>
> On 6/12/22 6:30 PM, Bob kb8tq via time-nuts wrote:
>> Hi
>>
>> Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For
>> bonus points, open up the crystal package. If you have the gear to test it, take a look
>> at what the gas *is* inside the package. ( Good luck with that :) :) :) )
>>
>> If you had the gear and the willingness to scrap out OCXO’s you would find that a number
>> of fast warmup OCXO’s have a *tiny* amount of He in the package. Measuring this would
>> be tough ( it’s that small). Go through the thermal modeling and it’s *way* more conductive
>> (thermal wise) than a *perfect* vacuum ……
>>
>> Bob
>
>
> And the worst thing is that if your vacuum sealed widget is in an atmosphere with more He around (like waiting for a launch, in a place that does more He leak tests, etc.), the He will diffuse into your package and it doesn't work like expected.
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
MD
Magnus Danielson
Mon, Jun 13, 2022 8:15 AM
Hi,
So, one of my hydrogen masers have a tiny leak. The outer vacuum does
not pump down as it should, and it has consumed the ion pump. This have
massive effect on the thermal balance and causes heat to leak out much
faster from the outer heaters to surrounding wall. This prohibits its
controllers of reaching the temperature but also prohibits next layer to
achieve it and finally inside that the actual resonator temperature
stabilization. That is in itself 5 temperature control-loops in 3
layers. There is also passive heat-shields in it. So, it is crazy
efficient heat transfer. It is so efficient method, that it's the basis
for pressure gauges, such as the Pirani gauge.
Now, while it is annoying it does not work, I can say that it has
significantly increased my knowledge about temperature stabilitzation of
hydrogen masers and workings of vacuum systems. Not to say I am fully
skilled, but at least not as ignorant as before, so there is a good
start. I also learned how to write some Python to log the serial port,
toss it into a InfluxDB and plots it with Graphana.
So the effect is real, very real.
We are looking into bringing a masspectrometer over, pump it down and
then do helium leakage tests to see if we can locate the joint that is
leaking. While there is many possible joints in the vacuum system, my
testing have helped to narrow it down to three. Of those, in particular
one could be suspect as it could potentially take more hit than the
others upon transport. Yes, I need a turbopump setup and spare parts.
Cheers,
Magnus
On 2022-06-13 03:30, Bob kb8tq via time-nuts wrote:
Hi
Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For
bonus points, open up the crystal package. If you have the gear to test it, take a look
at what the gas is inside the package. ( Good luck with that :) :) :) )
If you had the gear and the willingness to scrap out OCXO’s you would find that a number
of fast warmup OCXO’s have a tiny amount of He in the package. Measuring this would
be tough ( it’s that small). Go through the thermal modeling and it’s way more conductive
(thermal wise) than a perfect vacuum ……
Bob
On Jun 12, 2022, at 9:18 AM, Ross P via time-nuts time-nuts@lists.febo.com wrote:
I have seen that manufacturers seal their crystals in a vacuum, maybe air interaction affects Q. The point that vacuum inhibits heat flow is something I have never considered in ovenized units. My ovenized crystals take about an hour to settle. I have some WW2 surplus crystals in non-sealed packages that I have not tested... something to do.rp
On Sunday, June 12, 2022 at 07:26:19 AM PDT, Louis Taber via time-nuts <time-nuts@lists.febo.com> wrote:
I have been of the impression for years now that most "better" crystals are
in a vacuum. And the electrical and mechanical connections to the quartz
itself place as little mechanical load on the crystal as possible.
Thermal conductivity from the oven to the crystal itself would be both
hard to model and hard to speed up.
IR transmission of energy to the crystal also seems problematic considering
the IR transmission of quartz and the IR reflectivity of gold
contact plating.
Is any of this an issue?
On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <
time-nuts@lists.febo.com> wrote:
Hi
On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <
time-nuts@lists.febo.com> wrote:
On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
time-nuts@lists.febo.com> wrote:
On the subject of rapid warm up. I suppose if you had a need, one
could
dump as much power as you need into the heater. Turn on oscillator,
lights in room dim for a few moments.
Is that not likely to damage a crystal? Different parts of the crystal
and likely to be at significantly different temperatures at the same time,
putting a lot of stress on the crystal due to a thermal gradient. It's
probably a bit academic, as nobody is going to make an oven that heats up
in fractions of a second, but if one did, I suspect it might not do the
crystal a lot of good. This is only an educated guess - I don't have
anything to back it up.
Oh, it would be disastrous, although quartz is pretty strong, all the
rest of the mounting components might not be.
Indeed, breaking a quartz blank via thermal stress would be very hard to
do.
The “rest of the parts” actually are pretty durable as well. Most of it is
metal and
it is quite able to handle thermal issues.
The big issue in a fast warm up AT turned out to be designing the heater
and the
mount to get the energy to the blank quickly….. If you use a small enough
package
and blank, the amount of power turns out to be surprisingly small.
If you want to go bonkers, you mount the heaters inside the crystal
package. This
does indeed create some issues in various areas.
Bob
At the other extreme, would there be any advantage in actually heating
the crystal very slowly, over the course of an hour/day/week, so the
temperature gradient across the crystal is very small? Of course, if an
oven took ages to reach the correct temperature, it would be inconvenient
for most applications, but for some applications, the advantages might
outweigh the disadvantages. Of course, if one does this, I suspect one
would have to cool the crystal slowly too to prevent a significant thermal
gradient across the crystal.
I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
I was told that Nikon cools the front element over a period of 6 months to
reduce stresses in the glass.
Big glass mirrors for telescopes do the same.
Dave
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
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Hi,
So, one of my hydrogen masers have a tiny leak. The outer vacuum does
not pump down as it should, and it has consumed the ion pump. This have
massive effect on the thermal balance and causes heat to leak out much
faster from the outer heaters to surrounding wall. This prohibits its
controllers of reaching the temperature but also prohibits next layer to
achieve it and finally inside that the actual resonator temperature
stabilization. That is in itself 5 temperature control-loops in 3
layers. There is also passive heat-shields in it. So, it is crazy
efficient heat transfer. It is so efficient method, that it's the basis
for pressure gauges, such as the Pirani gauge.
Now, while it is annoying it does not work, I can say that it has
significantly increased my knowledge about temperature stabilitzation of
hydrogen masers and workings of vacuum systems. Not to say I am fully
skilled, but at least not as ignorant as before, so there is a good
start. I also learned how to write some Python to log the serial port,
toss it into a InfluxDB and plots it with Graphana.
So the effect is real, very real.
We are looking into bringing a masspectrometer over, pump it down and
then do helium leakage tests to see if we can locate the joint that is
leaking. While there is many possible joints in the vacuum system, my
testing have helped to narrow it down to three. Of those, in particular
one could be suspect as it could potentially take more hit than the
others upon transport. Yes, I need a turbopump setup and spare parts.
Cheers,
Magnus
On 2022-06-13 03:30, Bob kb8tq via time-nuts wrote:
> Hi
>
> Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For
> bonus points, open up the crystal package. If you have the gear to test it, take a look
> at what the gas *is* inside the package. ( Good luck with that :) :) :) )
>
> If you had the gear and the willingness to scrap out OCXO’s you would find that a number
> of fast warmup OCXO’s have a *tiny* amount of He in the package. Measuring this would
> be tough ( it’s that small). Go through the thermal modeling and it’s *way* more conductive
> (thermal wise) than a *perfect* vacuum ……
>
> Bob
>
>> On Jun 12, 2022, at 9:18 AM, Ross P via time-nuts <time-nuts@lists.febo.com> wrote:
>>
>> I have seen that manufacturers seal their crystals in a vacuum, maybe air interaction affects Q. The point that vacuum inhibits heat flow is something I have never considered in ovenized units. My ovenized crystals take about an hour to settle. I have some WW2 surplus crystals in non-sealed packages that I have not tested... something to do.rp
>>
>> On Sunday, June 12, 2022 at 07:26:19 AM PDT, Louis Taber via time-nuts <time-nuts@lists.febo.com> wrote:
>>
>> I have been of the impression for years now that most "better" crystals are
>> in a vacuum. And the electrical and mechanical connections to the quartz
>> itself place as little mechanical load on the crystal as possible.
>> Thermal conductivity from the oven to the crystal itself would be both
>> hard to model and hard to speed up.
>>
>> IR transmission of energy to the crystal also seems problematic considering
>> the IR transmission of quartz and the IR reflectivity of gold
>> contact plating.
>>
>> Is any of this an issue?
>>
>> - Louis
>>
>> On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <
>> time-nuts@lists.febo.com> wrote:
>>
>>> Hi
>>>
>>>> On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts <
>>> time-nuts@lists.febo.com> wrote:
>>>> On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
>>>>> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
>>> time-nuts@lists.febo.com> wrote:
>>>>> On the subject of rapid warm up. I suppose if you had a need, one
>>>>> could
>>>>> dump as much power as you need into the heater. Turn on oscillator,
>>>>> lights in room dim for a few moments.
>>>>>
>>>>>
>>>>> Is that not likely to damage a crystal? Different parts of the crystal
>>> and likely to be at significantly different temperatures at the same time,
>>> putting a lot of stress on the crystal due to a thermal gradient. It's
>>> probably a bit academic, as nobody is going to make an oven that heats up
>>> in fractions of a second, but if one did, I suspect it might not do the
>>> crystal a lot of good. This is only an educated guess - I don't have
>>> anything to back it up.
>>>> Oh, it would be disastrous, although quartz is pretty strong, all the
>>> rest of the mounting components might not be.
>>>
>>> Indeed, breaking a quartz blank via thermal stress would be very hard to
>>> do.
>>> The “rest of the parts” actually are pretty durable as well. Most of it is
>>> metal and
>>> it is quite able to handle thermal issues.
>>>
>>> The big issue in a fast warm up AT turned out to be designing the heater
>>> and the
>>> mount to get the energy to the blank quickly….. If you use a small enough
>>> package
>>> and blank, the amount of power turns out to be surprisingly small.
>>>
>>> If you want to go bonkers, you mount the heaters *inside* the crystal
>>> package. This
>>> does indeed create some issues in various areas.
>>>
>>> Bob
>>>
>>>>> At the other extreme, would there be any advantage in actually heating
>>> the crystal very slowly, over the course of an hour/day/week, so the
>>> temperature gradient across the crystal is very small? Of course, if an
>>> oven took ages to reach the correct temperature, it would be inconvenient
>>> for most applications, but for some applications, the advantages might
>>> outweigh the disadvantages. Of course, if one does this, I suspect one
>>> would have to cool the crystal slowly too to prevent a significant thermal
>>> gradient across the crystal.
>>>>> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens.
>>> I was told that Nikon cools the front element over a period of 6 months to
>>> reduce stresses in the glass.
>>>> Big glass mirrors for telescopes do the same.
>>>>
>>>>
>>>>
>>>>> Dave
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