[time-nuts] Helium leaks

[ed breya]

Jim,

The He and H2 can depart from inside the device just as easily as they 
entered, so if put back in a normal environment, the diffusion will 
reverse and eventually stop at a new equilibrium point. If the parts are 
exposed to the nice high vacuum of free space, they should ultimately be 
"cleaner" inside, than when in our atmosphere.

I could picture that a temporary excess of some species may upset 
operation, but eventually it should return to normal, unless some 
irreversible change or damage has occurred. I think I'd worry more about 
H2 (or even D2) leaking into an ionized-gas mix type of device (like Cs 
or Rb), and maybe reacting chemically. The He should remain inert and 
not leave any reaction products, and will depart eventually.

In a device like a MEMS, there would be no opportunity for chemical 
reactions, and any excess H2 or He should return to background levels, 
with no harm done. I suppose it's possible for some H2 to "stick" in/on 
some MEMS structure parts, depending on what they're made of, and 
increase their mass, but it seems probably a very tiny effect if any.

Ed