[time-nuts] It is possible to "recharge" a hydrogen maser?

[cdelect at juno.com]

Luiz,

Found some more info on replenishing the Hydrogen in the Kvarz CH1-76 and
CH1-75.

Anders had the procedure pretty close for a fully charged canister from
the vendor.

However recharging the original is a bit more challenging!

Use care and protective gear from the high and low temperatures involved!

Here are added steps somewhat paraphrased:

- open up (HFO, mag-shield etc.) enough to have access to the H-canister
- open the insulation around the canister and remove it from its oven.
- disconnect the canister from the Maser. (Threaded connector)
- connect canister to a manifold and vacuum pump and pump it down for 24
hours. 
- make an oven and heat the canister to 300 Degrees C for another 24
hours while still
 running the vacuum system
- Close off valves to isolate the evacuated canister and remove vacuum
pump.
- Attach a hydrogen regulator set to 240PSI to the manfold and purge the
lines up to the
 isolating valve.
- Open the isolating valve and leave the hydrogen connected to the
canister 
- the canister should get warm as it charges, you can blow cold air on it
to help.
- Once the cannister no longer heats and has cooled down close off the
Hydrogen valve.
- Also close the isolation valve to the canister.
 
Now here I'm not sure as I would think there is a step to purge the air
from the Maser lines.
Not sure how that would be done?

- with the canister still connected and the isolation valve closed
immerse the canister in liguid
 Nitrogen until it stops boiling off, then wait 5 more minutes.
- now while the canister is still cold remove it from the manifold and
reconnect it to the Maser.
 (Gloves Please!!!!)

At this point once the canister comes back up to room temperature you
would be ready to leak 
test and reassemble the Maser.

I'm actually working with a friend to install a new Hydrogen system into
a CH1-76.
NO LN2 or 300 Degree temperature involved!
The new system will be outside the shield and use a commercial hydride
canister.
A Solid-H BL-18.
Here is the rough outline for it's installation.

- open up (HFO, mag-shield etc.) enough to have access to the H-canister
- open the insulation around the canister and remove it from its oven.
- disconnect the canister from the Maser. (Threaded connector)
- mount the new fully charged canister with its attached valves on the
bottom right underside of the Maser
 (charging the new canister is similar to that detailed above)
- run the new hydrogen line to where one of the slots in the shield will
be.
- Screw the Maser hydrogen line onto the new lines fitting.
- Attach a vacuum pump to the 1/4" hose barb on the purge valve 
- Run the pump and open the purge valve. Wait 20 minutes to purge the
line.
- close the purge valve and remove the vacuum pump
- Open the canister valve to allow Hydrogen into the Maser.
- leak test the lines and reassemble the Maser.

Pictures and more details will be showing up in the EEVBlog Metrology
forum.

Keep in mind that since you have more room in the CH1-75 you could
probably install a small
compressed Hydrogen bottle and regulator instead of the Hydride storage
outlined!

Cheers,
Corby